Aquaponics Systems for the Freshwater Tropical Fish Keeper

by Steve Pond

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Copyright © 2013 Steve Pond

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First published 2013

Printed in the United States

Table of Contents

1. Introduction

2. Understanding Nitrate

3. What aquarists need to know about soil-less indoor gardening

4. Aquaponic Filtration

5. Aquaponic solutions for the aquarist - Bringing it all together in the home

6. Meeting the requirements of Freshwater Tropical Fish

7. Growing Organic Plants in the Filter

8. Parts to build your own system

9. A DIY Aquaponics filter

10. Fish to consider

11. Conclusion

12. Resources

1. Introduction

Aquaponics is the joining of two living systems much as they occur in nature - interweaving the two systems provides massive benefits to both environments and you benefit greatly because of it.

Aquaponics combines the rearing of fish in an aquarium with the growing of live plants outside the aquarium. Each provides for the needs of the other.

Here’s how it works:

You feed the fish properly...

The successful system then provides:

Crystal clean water and plenty of dissolved oxygen for fish.

Water, air, and enough of the proper nutrients for plants.

Essentially what you do with an aquaponic system is to extend your use of a biological filter to remove also nitrates and mineral type deposits that commonly cause the need for water changes.

The addition of an "aquaponic filter" will allow you to grow a wide variety of plants while providing clean, crystal clear water for the fish.

When set-up appropriately, even a 2 foot fish tank will easily grow a variety of vibrant plant life.

You can enjoy nutritious, organic vegetables and herbs and beautiful plants along with freedom from water changes.

This book focuses on a multitude of ways that an existing home aquarium can be adapted to an aquaponic filter.

We are, first and foremost, aquarists.  We enjoy keeping freshwater aquariums and watching our fish as they swim.

By the end of this book you will know how to incorporate the needs of growing plants and raising healthy vibrant fish in an integrated system that fully provides the needs of both.

2. Understanding Nitrate

All living organisms need adequate moisture and a suitable and healthy habitat to grow.  The common denominator between the fish and growing plants is nitrate - NO3.  An aquatic environment will create large amounts of it - especially if the system is closed like an aquarium.  The plants need it as the fundamental building block to grow and thrive.  The fish will become weak and diseased if it concentrates in their home to high levels.

The classic way to remove nitrate from an aquarium, at least for the past 50 years we have been keeping fish, has been to dilute it.  The two main reasons a partial water change must be done on a regular basis are:

1) dilute the nitrate produced by the biological filter

2) maintain steady water conditions by diluting other chemical build-ups such as carbonate and other hardness minerals that remain in the water after evaporation.

Until I found aquaponics as a filter, there was not a reliable way to remove the nitrate from the closed aquarium easily, or without considerable effort.  There are resins and all kinds of devices that will remove some, but nothing reliable or safe for the fish.  In most previous methodologies a part of the system needed to be turned anaerobic - deprived of oxygen. Certain bacteria do remove nitrate that way.  The problem is that all sorts of noxious gases are produced.  These can harm the fish if released accidentally.

We view aquaponics as a filter for an aquarium.   Commercial aquaponics simply uses the aquarium as the production factory for the nitrate needed by the plants. The plants, in turn remove the nitrate and return purified water to the fishes habitat.  Our job is to design a system that will deliver nitrate produced in the aquarium to the roots of the plants.  The roots suck the nitrate into the plant as fertilizer.  Purified water is returned to the aquarium.

It doesn't really matter where your focus is, on growing an organic garden or keeping the fish in the best health they have ever known.   The combination of the two is a powerful system that produces astounding results.

3. What aquarists need to know about soil-less indoor gardening

The needs of the plants:

air

water

rooting substrate

nutrients

Air - Plants require oxygen and carbon dioxide.  Both are components in the water where fish swim.  Carbon dioxide is used during photosynthesis and is combined with other elements to form sugars, usually in the leaves of the plant.  During this process oxygen is produced.

When light is not available, the process is reversed. Like other lifeforms, the plants require oxygen and will then give off carbon dioxide. Unlike an aquatic plant, however, there is no lack of oxygen in the atmosphere.

There is no oxygen deprivation possible during the late evening, which can be the case with a heavily overgrown aquarium with lots of strong aquatic plants.  Morning kill is the result of a heavily planted fish tank demanding so much oxygen during the very early morning that the fish are suffocated.

Over-planted tanks may use most of the nitrate created in a tank, but will usually require added carbon dioxide to be infused and possibly even an air pump to break the surface and allow oxygen to enter to prevent morning kill.

Water - One of the most common pieces of advice I offer to new aquarists is not to waste the water when a partial water change is performed.  The [dirty] water from an aquarium has lots of trace elements, especially nitrate, in it.

It is a wonderful elixir for houseplants. Instead of pouring the dirty water in the bucket down the toilet, it should be spread over the home's live plants to help them grow strong.  The magic is that the solution contains great fertilizers and other trace elements that plants require.  Plain water will keep a plant alive, but used fish water will make them thrive.

Delivering the "dirty" water to the roots of plants on a regular basis will do a number of things.  The main one being to provide an ongoing source of nutrients to the plants.  There are a number of ways to do this.  Later in the book we will describe some of the most effective ways aquaponics can deliver water and vital nutrients to food plants you want to encourage.

Rooting Substrate - almost every plant has some form of root structure. The only exception to this is algae, which are found in bodies of water.   In the aquarium situation, these compete with rooted plants for valuable nutrients.   Land based plants require a substrate to root themselves and provide a way to stabilize the plant as it grows.  Most standard gardening methods use the earth to root plants. Then the nutrients are supplemented over time with chemically based fertilizers to make the growing medium stronger and more supportive for the plants being grown.

Aquaponic and hydroponic grow beds also need to provide a substrate for the roots to use to stabilize the plants.  There are quite a variety of mediums used.  We will discuss the one we find to be the best a little later in the book.  Sometimes the substrate will add trace elements, other times the selected medium is inert and simply provides a location for the roots to gain a strong foothold to keep the plant upright and properly oriented.

Nutrients - As mentioned previously, plants require a number of nutrients to survive and thrive.  Nitrate is the most important in most cases.  There are other compounds that are part of the solution that we call water.  Plants require a constant supply of the elements they need to grow.  These can be depleted over time.  In most cases the only thing provided to the plant is water on a regular basis.  The plants are required to withdraw the other nutrients they need from the ground they are grown in.

Hydroponics and aquaponics work efficiently for strong plant growth because they deliver a constant and even supply of the various nutrients the plants are using up.  Hydroponics does this by mixing chemical fertilizer elements in the growing substrate the plants are grown in.  There is no guarantee that the compounds are non-toxic or harmless to the plants or the animals that digest them.  That strictly depends on the way they are mixed.

Aquaponics has healthy safeguards built right in.  The fish must be able to live with any chemicals added to the system as a whole.  In our illustrations, this is a flow through system, so anything added to the growing area will reach the fish almost immediately.

We will not be adding any external nutrients to the habitat.  The growing elements that the plants receive will be strictly derived from the wastes of fish.  As such all the nutrients will be indirectly delivered from the food the fish are fed.   We are assured that when the fish are properly fed, their wastes and other sources of ammonia will be degraded into nitrate.  This is delivered to the plants in its most highly digestible form for the plants being grown above.

The bacteria that produce nitrate in the home garden are the same strains that are vital for a strong biological filter in any water system - aquarium, a lake or stream.

Most aquarists are well aware that underwater plants will add noticeable amounts of oxygen to the environment when they are photosynthesizing in the presence of a strong light.  They may even know that plants remove some nitrate for their growth as well.  But rarely are there enough aquatic plants available to remove all the nitrate the fish produce in an aquarium.

When you move the growth up and out of the tank, the terrestrial root structure can purify the toxins outside the fish tank. This makes the returned water to the aquarium safe for fish to live indefinitely.

4. Aquaponic Filtration

We are certainly not the first to promote bringing live plants into the home for added nutrition and flavours in the kitchen.  There are a few things to keep in mind when developing an aquaponics filter for your home aquarium:

An aquaponic filter puts the focus on the fish

The activity within the aquarium is where the interesting action is.  Watching lettuce grow is as exciting as watching paint dry. However, observing the little fertilizer factories zoom around is a whole different ballgame.

The life an aquarium brings into a home is a very important advantage.  If we are to get an aquaponics unit accepted into the living space of the home, the system must be pretty enough to enjoy watching.  It must have the potential to become a focal part of the room it is located in.

Plant growth will be limited to the available nutrients generated by the system.  A single goldfish or Betta may be quite comfortable in an aquaponics system designed for it.  Especially since all of the nitrate produced will be rapidly used by the plant(s).  But the life processes of a single fish will not be enough to sustain plants over an extended period.

We are going to focus on aquariums that can house a useful number of fish, starting with a 12” x 24" rectangular frame.  The concepts developed and discussed here are meant to be scalable to tanks as large as 18" x 48".

Purifying the water

The aquaponic filter is going to do a lot of the actual filtration required by the system.  It introduces the dimension of nitrate removal.  This extends the biological activity all the way to final elimination of nitrate from the water.

If the aquarium is already established and you are assembling a retro-fit system, chances are that you can keep the present filtration system with no problem at all.  Aquaponics filters reduce the maintenance required for an aquarium.  They improve the water purity.

If the tank is not set up yet, some different filters from the standard recommended unit might be considered.  The Undergravel filter has fallen from favour recently due to the abundance of canister and other self-contained power filters.  However the biological strength of this type of filter is a major benefit for an aquaponics system designed from the ground up.  It turns the entire substrate of the aquarium into an efficient bacterial filter.

The problem with this style in an established system is that it is extremely dirty to install one in an established fish tank.  The plates must be placed under the existing gravel.  It is much easier to install when the system is first being set up.

It is much easier to add an internal power filter. I supplemented with a small Fluval  "Nano" filter.  This uses only a couple of pieces of foam.  They become extremely bacteria friendly over time.  The output is a spray bar so there is plenty of surface agitation to ensure oxygen and carbon dioxide exchange in the aquarium.

Air driven sponge filters have been used quite extensively in fry tanks where the babies are tiny and unable to get away from the suction of most other filter styles.  Vibrator air pumps can become quite noisy.  Air bubble breaking the surface also provide a background noise that can bother some people as well.

It was cheaper to purchase a motor driven internal system, rather than add an air pump and inside sponge filter.  The pump is much quieter than a standard air pump. The only noise created by the "Nano" filter is the spray bar when evaporation drops the water level too low.  The choice between power filter and sponge filter is a personal one.  Either will go biological quite fast, while removing some particulates as well.

Established aquariums, or starter kits that come with filtration should be examined for suitability.  I suggest the use of an outside power filter such as the AquaClear line, or a versatile canister filter where the choice of filter media is left up to the aquarist.  Whatever filter you use, remove and eliminate all exotic filter media, especially carbon.

Carbon has long been a controversial media when aquatic plants are included in the habitat.  It is rarely regarded as a viable material for filters in Europe because of the heavy reliance on live plants in their aquariums.  Research has shown that activated carbon adsorbs a multitude of trace elements from the water.  Many are required by plants. Since these are important to plant health, it makes no sense to use it in any aquarium that will be fitted with an aquaponic filter.

The same can be said for most of the other specialized media and resins that have been developed to improve the aquatic habitat.  Stay away from Zeolite in any form.  Zeolite acts as a resin to trap ammonia, since that is a precursor to nitrate, this is not useful.  The same can be said of some of the other materials like phosphate remover and nitrate remover.

In my experience with retrofitting an aquarium with an aquaponic filter, the only changes to filtration that need to happen is that all activated media be eliminated.  Let the plants trap and incorporate the impurities that normally would be removed by aquatic filter media.   Provide as strong biological area as possible at the same time to make the production of nitrate as efficient as possible

I prefer to rely on the most common inert media formats.  Foam inserts are quite useful to trap both debris and provide colonization nodes for the beneficial bacteria. If you want a dedicated biological filter area,  create a fine screen to prevent small particulate debris from clogging dedicated biological media.  These could be sintered glass or porous ceramic rings, nodes and cylinders.  These require a dedicated bio-filter area.

5. Aquaponic solutions for the aquarist - Bringing it all together in the home

In this book, aquaponics systems are approached from the aquarist's point of view, not a gardener's perspective.  Because of this, the growing pan is defined as the aquaponic filter.  It must perform a number of jobs.  It must provide the growing area for the herbs and vegetables.  It also must provide the reliable removal of nitrate from the fishes living area.

Traditional aquaponics uses a number of different systems to accomplish this. We will examine the most important so that you can understand why we have opted for the style we advocate for home aquarists.

1) Flood and Drain

Provide intermittent flows of water into a substrate filled pan for a few minutes at a time.  The pump then cuts out.  When this occurs, the water is allowed to slowly drain back into the fish tank.  The water level in the pan rises and falls.  This gives the plant roots a bath of nutrients intermittently.  It is not very easy or efficient to create a reliable flood and drain system for the home aquarist.  It requires timing pumps and often needs assorted valves as well.

Flood and drain systems fill the growing pan with substrate to root the plants anywhere within it. While this may be an advantage for some, the fact that the pan is filled with a growing medium like expanded clay pellets makes it quite heavy.  We are looking for a system that goes vertical above the aquarium. Variable weight between flooding could make this difficult to support without too much stress to the fish tank from above.

Flood and Drain systems require complex timers to ensure the water rotation is reliable.  Few aquarium pumps are able to perform this constant on; then off; cycling.  Aquarium and pond pumps are designed for constant use.  Few pumps can be turned on and off this often without causing wear and tear problems. Many cheaper pumps may not even be able to be properly controlled.

The intermittent flow for flood and drain systems also means there is minimal water movement.  The water that does return often comes in spurts - this is not good for fish.  This type of system is much better for multiple grow beds where enormous water flows are required and can be directed back into the fish vat with a constant flow.

The most worrying problem here is the weight that will be applied above the featured fish tank.  Not only will the growing pan be full of heavy substrate in this style of aquaponics, the actual weight will rise and fall as the grow pan fills and drains out.

We are looking for lightweight growing systems.  They should not approach the load bearing capacity of the aquarium which provides the support for both the grow bed and the artificial lighting placed above it.   Our designs are vertical, so the weight will rest directly on the top of the aquarium. The closer we can stay to the weight of a standard aquarium canopy, the better.

2) Constant low flow system

In our experience, the low flow system is the better choice as an aquaponic filter for the aquarist.  The only weight is the thin water layer and the weight of the net pots and pans. Of course there is also the added weight of the artificial light used to grow the plants above the aquarium.

A low flow system delivers a constant water flow to the plants.  This means the filtration is always active for the fish and the aquarium.  The water is always in constant motion through the entire system.  This prevents stagnant areas or places where the system can go anaerobic.

Roots are always kept in constant contact with nutrient solution.  The nitrate in the water circulates through the growing pan continually.  Any other trace elements and nutrients are also constantly provided through the water flow.  This exposes plants constantly to the nutrients created by the fish.

Any filtration system is more efficient when it works constantly. This is especially true for any biological unit.  An important requirement is a constant supply of oxygen to the bacteria.  If water flow should stop, it takes very little time before the bacteria use up the available O2 and suffocate.  A fully matured Undergravel filter will die off in the first hour of a power failure.  Closed canister systems have about the same longevity in a power failure as well.

Another strong advantage of a constant low flow system is that it can employ discrete net pots. These hold the plants without having to completely fill the volume of the growing pan.  This eliminates a lot of weight.  There is much less danger of developing a problem from the dead weight on the upper frame of the aquarium with these systems.

Of course a low flow system is possible through a fully filled grow pan.  However, that is not the model the authors feel may be the most efficient style to position above a typical home aquarium.  The aquaponic filter can grow a variety of vegetables and herbs, but it should not be expected to grow large and bushy plants.  The types of plants that will do best in the home have shallow root systems and do not need as much depth to thrive.  They are quite suitable for the type of aquaponic filter that will be outlined below.

6. Meeting the requirements of Freshwater Tropical Fish

People who keep fish for any length of time need to understand their specific needs to be successful.  For those not as familiar with their maintenance, there are a few factors that must be satisfied for them to thrive.

1) Food - Most fish eat similar foods, or at least they can be maintained in good health with a formulated staple diet.  There are specific diets for some families, and the temperature of the water has a great deal to do with the amount of protein they require.  The food given to the fish is the energy added to the system not only for the fish, but the plants as well.

There might be a tendency to try to over feed the fish to ensure that there are lots of nutrients in the tank for the bacteria to break down.  Don’t fall prey to the concept that overfeeding seems to be justified.  Although this may seem logical, it is not true.

You can (and probably should) increase the food given to the fish somewhat.  Usually this is most efficiently accomplished by adding a second regular feeding period per day.  Standard aquarium feeding is to feed once a day.  Offer as much food as the fish can eat in two minutes with nothing left over.  In the Aquaponics case, it can be increased to a couple of times a day.  There should always be the restriction that nothing is left over after the two minute interval.

Overfeeding leads to very poor water conditions.  Fish will suffer. If the fish are not healthy or thriving in the system as a whole, the plants will not get what they need as a result.  The fish digest and break the food down.  Too many harmful products are produced when fish food is allowed to rot without the intervention of fish. Although regular feedings twice a day are encouraged– over feeding them to the point where wastes lie on the bottom uneaten is not.  Simple decay has not been found to benefit the plants using the fish water in any identifiable way.

2) Water Replacement - In a thriving aquaponics system, the water is constantly circulated throughout the fish tank.  It is then lifted to the grow pan and exposed to air for an extended duration.  Water evaporation is common in all aquariums.  It becomes much more so when growing plants are introduced.  Granted, much of the increased water loss may not be directly due to simple evaporation. Water is also lost through the leaves of the plants.

Lost water must be replaced.  This is more important than at first blush...the plants will use a lot of water to grow.  But actually it is much less than if they were grown in soil - ten times less is the common wisdom at the present time. Since this is a precious and dwindling resource, conservation of water during growing will become increasingly important, both at home and commercially.

3) Light - light is needed to see the fish and also allow them to find food when it is offered.  When growing plants are moved outside the aquarium, the importance of lighting is reduced for the aquarium.  This does not mean that light should be eliminated.  The addition of an aquaponics filter will create a challenge for delivering light under the growing pan.  The characteristics of LED lighting make this a perfect place for this style of lighting to be installed.  LED strips generate little heat and they are extremely compact and versatile.  Compact enough, in fact, that one can be glued to the bottom of the grow pan with no negative consequences!

4) Oxygen - Aquaponics reduces the requirements for standard filtration.  Our system uses only a small water pump at the present time.  There needs to be enough surface agitation for oxygen to be replenished into the tank.  The water drop style of a suspended pan can easily produce the amount of surface agitation needed.   This allows gas exchange in large enough quantity to keep a large fish population happy.  Air pumps may be needed to supplement this as the loads get greater.  A secondary benefit of a constant low flow system is that the water circulating though the grow pan is also exposed to the air for an extended period as well.  There should be no lack of O2 in the aquarium.

5) Biological Filtration - There must be enough usable surface area for beneficial bacteria to develop into strong populations.  Beneficial bacteria also heavily populate the grow pan area as well.  These must reduce the ammonia and nitrite produced in the aquarium to nitrate for the plants to use.  The plants will remove nitrate in large enough quantities to purify the water as it passes through the grow pan.  Water is returned to the aquarium purified.

While there is no need to remove the standard filtration that is established on an operating aquarium, there are cases, occasionally, where the existing filtration will not be suitable.  An outside hang-on filter may not be easy to accommodate through the walls of a supporting aquaponic filter pan.  Should this be your situation, consider some of the older style filter systems.  Air driven undergravel filters and sponge filters can be easily inserted to provide the surface area for the beneficial bacteria to thrive.  Larger tanks will easily allow a power head to make an UG Filter even more efficient.

If the existing system contains a canister filter, it is usually easier to drill small hose openings for the hose assembly through the walls of the growing pan support.  This should not weaken the aquaponics filter support and will permit strong solid waste management at the same time.

I prefer to contain the filtration of an aquarium used to support aquaponic growth inside the aquarium.  This is purely a personal preference since I had a recent power failure where a canister leaked out half the tank through the seal ring.  I removed it and went with the aquaponic filter only with a strong load of fish in it.

Since then I have added a small inside sponge power filter (Fluval Nano Filter) with integrated spray bar.  The return is gentle enough for shrimp while providing strong surface agitation and extra biological surface area for improved nitrate production.

7. Growing Organic Plants in the Filter

Because the purpose is to grow natural foods, organic and heritage seeds are preferred over genetically modified (GMO) plants.  GMO is extremely controversial.  It may be the actual reason you are investigating the opportunity to grow some of your own food in the first place.  Monsanto and other large agricultural companies have no qualms in forcing GMO seeds onto standard farms.  This is in spite of the fact that the long term effects are unknown.

We could have a time bomb ticking in our food supply.  The aquaponic filter is exposed to much more than just nitrate, phosphate and potash.  The flowing water also brings micro-nutrients that are often exhausted or missing in standard farming practices.

It is for this reason I have been actively investigating the options we have to cultivate a reliable food source.  Like many others I am trying to become independent of the present agricultural establishment.  I no longer wish to rely on factory farm through the heavy processing of the plants and delivery to the supermarket.  An aquaponics filter can reduce the requirements, if only a little.

Herbs such as oregano, thyme, basil, sage and mint are ideal for the constant low flow systems.  Vegetables such as lettuce, kale, cabbage, mustard greens and even cucumbers are also suited for these optimized growing conditions.

One limiting factor for the entire system will be the height above the grow pan the lighting can be raised.  If the lights are not high enough, tall plants such as beans and other large bush like vegetables would be quite difficult to have consistent success indoors.

In the beginning the most success will be in herbs and micro veggies, the best will be ones with shallow root systems that can adapt to the net pot and constant flow of water across the exposed roots.

Herbs

Oregano, thyme, basil and sage mint, and rosemary

Vegetables

Lettuce, kale, cabbage, mustard greens, cucumbers

Fruits

Strawberries

Flowers

Most annual flowers have shallow root systems

Rhododendron, petunias, lavender, impatiens and zinnias

It is not reasonable to expect to grow corn or other tall plants in your home! If this is your aim, explore the possibilities using flood and drain with a permanent substrate of at least 12" in depth for the roots to grab a strong foundation.  These systems will scale up quite well.  They are rarely compact enough to become part of the inside household. Rather these systems are most economical and efficient when using the power of natural sunlight outside - assuming climate conditions permit.

In outside systems the use of worms in the growing media is also encouraged.  They provide excellent additional soil adjustment over time.  Solid substrates such as expanded clay pellets and/or crushed granite are good choices to fill the grow pan. The weight makes using the aquarium as the support for the grow beds risky.  It is better to support these situations with proper stands.

8. Parts to build your own system

Lighting

Plants must have adequate light. There are whole aquarium companies devoted to providing the perfect spectrum underwater. The same situation applies to hydroponic and aquaponic growing.  The cheapest, of course, is direct sunlight.  Often this is a serious problem for indoor aquariums.  Sunlight will cause green water - an algae bloom in the aquarium.

If natural light is a part of your plan, the system can be developed where there is no light striking the aquarium.  Possibly the aquarium can be located below the window sill, or the light can be fully blocked off.  Installation of a fully opaque background that blocks both the sides and the back from natural sunlight could be considered.  This could permit the sun to shine on the aquaponics filter.  Never expose the fish tank to the sun.

Artificial light is the most common method of providing illumination in the home situation.  There are many possibilities. These could include mercury vapour, metal halide and sodium bulbs. These have strong light spectrums, but all produce a huge amount of heat and are quite high on the energy consumption scale.  The costs of these possibilities are prohibitive to purchase, and should only be considered if such options are already installed.

Earlier, in chapter 2 under the heading Lighting is vital, the options for lighting of the aquaponics filter were discussed.  If at all possible, try to go with a minimum of T5 lamps.  As far as energy consumption and longevity, an LED system designed for the growing spectrum of plants is even better.  It will cost quite a bit more at the outset, but will provide the best light source for a very long time. The added benefit of almost no maintenance at all makes these fixtures the most appealing.

System stand

Selection of the light source is pretty much up to personal preference with only one caution. You want to make sure that the fixture you purchase can be supported by the light stand.

If you are quite handy with woodworking, you can build a stand for the pan and light around the aquarium This allows you to retain the present lighting.  Most people will opt to remove the present canopy and match the grow pan support and light stand to the actual tank frame.  This is the simplest solution for most aquarium installations.

Because the aquarium canopy is normally removed when adding a grow pan and support, an LED light strip is suggested to illuminate the fish. These can be purchased with a number of diodes in a strip format and glued with aquarium safe silicone or non-toxic glue to the bottom of the grow pan.  The support structure for the pan should be high enough to keep the lights dry above the water.

In most cases the light support stand can be made from square tubular pipes, and the fixture will be suspended from it by two clips.  A parts list is included later in this chapter.

It is important the stand is sturdy enough to hold the fixture securely and not be so tall as to become unstable.  This issue becomes more important the longer the tank that is retrofit.  A very easy stand for tanks up to 48" can be constructed using 9 pieces of square steel tubing, 2 "S" hooks, 6 corner fittings and 2 "T" fittings.  The only variance may be the size of the tubes and fittings, larger ones may be needed for longer tanks.

Water Pump

An aquaponics filter sits above the tank and is supported by the upper frame. Because of this, it must be as light as possible. The best solution for this restriction is to use the constant low flow style nutrient delivery system.

A water pump to provide constant flow is required.

These are quite common, and the best ones are fountain pumps designed to raise the water up at least 18" above the level of the fish tank with little loss in performance.  The actual head would probably be closer to 6 - 12 inches.

The flow does not have to be too fast. In fact it is dangerous when the water flow moves too swiftly.  The roots would have a harder time to pull nutrients from a rapid current.

The slower the water flows, the better, up to a point.  There must be a balance between the water pump's flow and the needs of the aquarium to keep the water moving and debris suspended.  This takes some observation and adjustment as time goes by.

In my experience, the best way to proceed is to start the pump at the lowest setting.  Then see how the growing pan and the return react. If the flow is too low, you then have the pump's full range to experiment with.

Fittings

You’ll need to connect the pump to the pan.  The fittings should be waterproof bulkheads where the

1) water enters the growing pan

2) where the water falls back into the aquarium.

Many fittings can be sourced in a swimming pool supply store or possibly a plumbing specialty store, or any of the big box home improvement locations.  In a 20 gallon aquarium, 1/2 to 3/4" connections are adequate.  It will usually depend on the water pump output stem.

If you have trouble finding an adequate input bulkhead, another option would be to use aquarium canister hose fittings to create a curve up and around the outside wall of the grow pan.  Let the water flow into the filter media.  There is some danger that the hose could become dislodged and fall out. You must ensure this cannot happen if you install this way.

The return bulkhead should be raised 1/8 of an inch or so above the grow pan's bottom.  This ensures the entire pan fills with water before it can drop out. There should be no dry areas on the bottom. The roots extending from the net pots should be evenly submersed in the slow flowing nutrient rich water.

The bottom tip of the net pot should be inserted into the water in the pan.  This ensures the substrate stays wet all the time.  The 1/8 inch space between bottom and drain is needed to control the depth of the grow pan water to allow this to occur.

Grow tray

A proper constant low flow system requires water to be passed through the grow tray at all times.  The most effective method is to work against gravity only once.  The most efficient use of space for the home aquarist is to mount the growing tray directly above the tank and allow the water from the growing area to return directly to the aquarium.

Designing the grow tray.  There are a number of ways to build the grow tray.  We will outline two that we like for this purpose.  Both replace the aquarium canopy entirely and cover the canopy area with the aquaponic filter.

The first style requires two food grade plastic pans. One serves as the support structure and the other is the actual grow pan.  The grow pan must be slightly smaller than the bottom dimensions of the support tray.  The support tray has most of the bottom removed to allow the grow tray to be inserted into the inverted support tray.

The support tray should be as closely matched to the actual dimensions of the aquarium as possible.  Both of these units should be made of food grade plastic and be completely inert to pH and aquarium water components.  The support tray would be placed on the bottom plate shown below.

The second style still requires obtaining a food grade plastic grow tray with dimensions slightly less than the actual aquarium footprint.  But instead of an inverted support tray of the same design, you might want to opt for a more stylish and utilitarian design.

In this case, there is no need to source a support tray of the correct dimensions.  This can be difficult depending on the actual footprint of your aquarium.  Instead, you can custom design the support for the growing trays.  For larger aquariums, this design is probably the one you will opt for.  It is simple and easy to outsource.  Chances of finding a suitable support tray in the exact dimensions of the aquarium are not that great.

9. A DIY Aquaponics filter

The figure below shows a possible set of cuts on a single piece of material that will produce the main parts of a DIY Aquaponics filter for a 24" x 12" aquarium.  Some adjustments would be required to create a similar system for a 30, 36 or 48" long aquarium.

This design requires a couple of plates of acrylic that are slightly larger than the actual dimensions of the aquarium.  For those just trying this as an experiment, you can opt to use 3/8" to 1/2" plywood sheets instead.  Just be aware that over time wood could become waterlogged and weaken unless you protect it with a safe, non-toxic paint.

When dealing with acrylic, the easiest material to find is clear.  We suggest making the extra effort and expense to obtain opaque material.  You do not want uncontrolled light to enter the aquarium or the growing tray.  It will promote growths of algae that are both unsightly and unwanted.

You will need three sheets of material in all, plus a few dowels of at least an inch or so diameter.  Some of the excess pieces can be used for decoration and added structural strength.  The last part is the growing tray that holds and directs the water for the plant roots.

The Bottom Sheet

The bottom sheet is the base of the system. It will sit directly on the aquarium frame or the top edges of bare glass if the aquarium you have is frameless.   It should overlap the aquarium frame by a quarter inch at least to ensure it will sit firmly on the tank.  It should have the inside area cut out, leaving about 1" to 1 1/2" of material to form a ring around the frame of the tank with the center wide open.  This design is suitable for smaller tanks where water pressure creates negligible bowing.

Compensate for Bowing

For tanks larger than 30", you will need to take the weight and pressure of water on glass into consideration.  Do not simply take the dimensions of the aquarium from the manufacturer's sheets, or before the tank is properly filled. Remember that water in any aquarium will cause a bow to happen. The aquarium should be filled and measured, especially in the middle to determine how much bow the tank will have when filled.

If the ring is cut without regard to the aquarium bow, there is a good chance the tank will be too wide for the ring.  This could result in parts of the tank sticking out under the ring and causing problems in support of the grow tray above.  This is the same problem that many aquarists have encountered when fitting sliding glass tops, and one to be carefully avoided.

When designing the dimensions of the top plate, we recommend making the top ring a bit smaller in overall dimensions - up to an inch less in both length and width.  This allows the light stand to be placed on the bottom tray without any interference from the top plate.

The dimensions of the light stand should be such that the basic weight of the stand and the posts used are sitting as much as possible on top of the tank frame itself. You do not want the weight of the stand hanging over the edges and placing stress on the bottom support acrylic ring.  Doing it this way uses the weight of the light fixture and stand to keep the entire aquaponic filter solidly in position.

The Light Stand

It may be useful to design and build the light stand prior to cutting the bottom plate to ensure the two are properly matched. Once you know the bow of the aquarium, make the light stand to take advantage of the entire footprint, you can use the inside dimensions of the light stand to provide the basis of the top plate's maximum outside measurements.

Parts for the Light Stand - Example for a 24" aquarium

Use square tubular steel - this is often used in standard aquarium stands. The square tubing in this example is 3/4"

5 x 23.5" pieces

(1 piece each for front and back = 2) (Attached by 1 90o elbow at each end)

(1 piece each for the side upright = 2) (Top Support attached by 1 90o Elbow at each end)

(1piece for Top Support - two 1/8" holes drilled 3" in from each end to attach "S" hook)

4 x 5.5"   pieces

(2 pieces for each side attached in the middle with "T" Facing up)

6 x 3/4" 90o elbows

2 x 3/4" "T" connectors

2 S hooks (Used to hold the T5 Double Grow Light fixture

The Top Sheet

The top plate should have the center cut out to accept the grow tray you have selected.

Do not cut the hole until you know the exact dimensions of the pan that will be fit into the opening.  You do not want to have to redo the plate because of changed measurements.

The Net Pot Holder

The net pot holder covers the grow pan.  It has openings cut into it to hang the net pots into the grow pan for moisture.  The net pot holder needs to fit securely over the grow pan.  This cover must be suspended above the water with the bottom of each net pot submerged slightly.

If the grow pan has a lip around the top, insert it into the pan using the sides to hold it up.

If the grow tray does not have a lip, ensure the cover is large enough to rest on the entire top of the grow pan.  The net pot holder needs to be cut somewhat larger than the pan opening to completely cover it and ensure no light enters.

It is the support plate for the net pots.  It will have holes drilled in it to accommodate the net pots used to germinate and grow the seeds and plants.  Drill the holes only when you have obtained your net pots and know their exact dimensions.

Putting it together

You can use some of the excess material from the center to cut some support strips. These are used to give greater stability and warp resistance to the top plate.  Glue them lengthwise around the edges of the top plate to give the structure stiffness.  Properly positioned they should prevent sagging from the weight of the grow pan over time.

If you are using acrylic and cannot get acrylic dowels, another use of the material from the center hole is to cut and laminate four to six posts.  These are the spacers to glue between the bottom and top plates. If you are using wood, it is easy to find 1" dowels that can be cut to the right height to support the top and bottom plates and give room for the grow pan assembly.

Assuming the acrylic plates are 1/4", you may need three or four pieces per post.  The posts can also be acrylic dowels of about an inch in diameter. They should be cut between 4 to 6 inches long, depending on the depth of the grow pan.

You want the pan high enough above the aquarium surface to allow unhindered access to the aquarium.   These laminated posts should be glued to the four corners. You can add ones in the center, if necessary, to hold the two plates apart and prevent warping. The longer the aquarium, the more posts may be required to provide the stability needed to support the grow tray.

The growing area

The next design issue is to ensure the water getting into the grow pan is free from as much waste as possible.  The way this is accomplished in your installation depends on the material of the grow pan.  If you can glue a partition diagonally across one corner and place the input bulkhead inside, that is one option. A second option would be to install a circular dish, such as a plastic food tub that has been drilled into a porous grid to allow the water flow to exit with as little resistance as possible.  A thirds option would be to glue a partition at the entry area of the pump and force the water to flow through the foam before exiting around the plate and into the grow pan

You do not want the water to be able to rise above the partition and overflow it.

The input bulkhead should flow the water directly into the mechanical screen with little or no resistance.  The entire volume of the filter compartment should be filled with a loosely packed material to trap small particulates pumped up from the fish tank by the fountain pump.

Filter and bulkheads in grow pan

Fill the partition with a mechanical filter material. I use a foam, such as a reshaped AquaClear© foam to fill the entire volume of the mechanical sieve.  There are a wide variety of foams available, not all are safe for fish.  Be wise and repurpose a foam block that is meant to be used for aquarium filtration to be sure there aren't any unsafe compounds added to the tank.

The glued plate alternative should have the plate accept the desired [AquaClear© ] foam without it being loose or able to slide out. The water from the input bulkhead must travel through the length of the foam before it can move into the grow pan.

The return bulkhead should be raised slightly higher than the actual bottom of the grow pan. Space needs to be added between the return hole and the grow pan bottom.  Ensure that a thin film of water, at least an 1/8" to 1/4" thick covers the entire bottom of the pan.

If the selected grow pan is deeper than the net pots, extra depth may be required. You must ensure the bottom of the net pots are always submerged.

The water will rise and overflow the output and fall back into the aquarium.  The outlet should be positioned directly above the aquarium below it.  The waterfall effect is useful to break the surface tension of the fish tank. There should be no need to add hoses or complex return paths.  Let the water fall directly back into the aquarium.

The net pots we use are round with a diameter of 2" x 2.25" deep. The grow pan needs to be deep enough to accept the entire depth of the pot, with some room below to allow the rapid growth of roots into the pan.  Design the net pot holder to hold as many pots as comfortable.  Be aware that the roots will grow into the pan, so be sure there is some space between each pot hole.  Also, design the cover to ensure there is no overlap of the holes over the walls of the grow pan or the input and overflow assemblies.

Growing Media

This system will germinate seeds and support quite a variety of edible plants.  Most of these can be grown directly from seeds and harvested as they mature.  The best growing substrate to use is expanded clay media. This is one of the more popular media. It provides a good base for a large variety of plants.

The net pots have a flow through slotted design that allow the nutrient rich water to come into contact with the roots.  The slots also allow the roots to expand out from the substrate and grow into the passing water flow.  It has been suggested that a thin layer of crushed granite will slowly release a number of vital trace elements for the plants, but it can also increase the hardness of the water for the fish. If you opt for something like this, constant water testing for hardness is recommended

Starting plants

Many seeds will grow right in the growing media.  The bottom of the net pot should be immersed in the water flow, so the growing media will be moist at all times.  But this may not be enough.  There are two methods promoting the efficient germination of the seeds you select.

1)  The easiest way is to mist the pots on a regular daily basis.  This will ensure that water is available to soften and start the seeds growing.  You will need to keep this up until the roots of the seedlings reach the water flow below.

2)  Another way is to prepare the growing pot to pull the water up from the water flow. When preparing the new grow pot, use a piece of paper towel as a wick to draw water up to the upper levels.  Cut an inch wide strip about 4 - 5 inches long. Place the strip to cover the bottom of the net pot so it is immersed in the flow.  Draw the strip up the side of the container.

With the wick in place, fill the pot about half way, then lay the rest of the strip across the pot.  Add another thin layer over the strip and fold the rest of the strip back over the layer.  Mist the paper towel strip to get it damp and start the wick working. The seeds can be put directly on the damp paper.  Do not overcrowd the seeds on the paper.  10 seeds or so is plenty for most plant types.

10. Fish to consider

In classic commercial aquaponic systems, the fish that are raised are part of the economic equation. They are rarely watched, and grown out to a size that can be sold for the table.  In most cases these are domestically raised tilapia.

These fish are perfectly suited for a commercial operation. They grow rapidly and are becoming more and more popular as a dinner menu item.  In some areas, though, these are against the law to possess and not available for the aquarist.  Tilapia are very hardy and will adapt to a variety of water conditions.

There have been enough instances of release into the wild that they have become pests to native habitats.  Tilapia may not be available for sale in a local pet store near you because of this.  Southern California has strict laws about keeping them. Even as far north as Michigan has will not allow you to keep them - even though they will not survive such a harsh winter.

But the purpose of this book is not to develop a commercial aquaponics system.  We are trying to bring the enjoyment of growing fresh vegetables and herbs to the home aquarium.  The ability of the system to remove nitrate and many other compounds that tend to build up in the ordinary community aquarium allows somewhat heavier populations of fish.  We do not recommend overstocking the aquarium. However, the plants will purify the water much better than many other filter systems.

Because of this, most of the fish communities that are presently kept in established aquariums can continue and thrive when an aquaponic filter is retrofitted.  That is the way one of my systems was installed.   Almost any fish will do. So, if you have a tank with an established community, there is not really any reason to modify the inhabitants.

When you are starting out the aquarium, though, there are preferred species to keep.

The most important consideration is the size of the aquarium.  A smaller aquarium requires fish that remain small as well.  It has been determined that one pound of fish in the aquarium can produce up to 70 pounds of vegetables and herbs.  The type of fish are not really that important as far as the vegetation is concerned, they really have no interaction with one another. The weight being housed makes a difference in the amount of available nutrients.

Standard community fish are quite capable of providing the nutrients required.  Start the aquarium the same way as with any other filtration installed. Use hardy fish, such as recommended in our previous book The 7 Best Beginner Tropical Fish Species to start a New Aquarium.  This short book outlines the various families and species that will be best to start a new aquarium system.  The only difference is that when considering aquaponics systems, it is better to add fish that have more bulk.  Stay away from thin and fast, in general.

A new aquarium should never start with more than 1" of fish per gallon, and after the biological filter has fully matured, the limit rises to 2" per gallon, at least in my experience.   Don't add them all right at the beginning.  Take your time and build the population gradually to the full load.

Although you can use almost any fish to support the aquaponics filter, it is better to select fish that grow larger with more body bulk.  Always select fish that will be comfortable within the particular size of your tank over the long run.

Species to consider when installing an aquaponics filter:

Tilapia

The most popular, as previously mentioned, are Tilapia. There are quite a number of fish under the umbrella of Tilapia - all of them are part of the cichlid family discussed below. The most popular is the Mozambique Tilapia. It is hardy, grows rapidly and as a mouth brooder breeds and repopulates rapidly. It is ideal for many commercial installations, but is not particularly colourful or exciting to watch as a single species tank.  It truly depends on your personal goals whether Tilapia are worth consideration for your home tank.

Goldfish

A second fish that can be quite useful are the common goldfish.  They are cheap to buy, require no heat, and prefer room temperature or cooler water.   They will grow somewhat slower. In small home tanks they rarely reproduce. They will spawn in ponds and water gardens if they are large enough.

A common comet will grow to a size that will often outstrip the aquarium.  It might be wise to plan how the fish can be removed to other homes. If you have an outside pool, this may be perfect.

Koi

The same considerations apply to Koi -they are also carp like the common goldfish.  However they often will grow quite a bit larger - a foot to three foot Koi is not unknown. They should be considered only if the fish are in a large container or can be given away to someone who owns an outside water feature.  They grow slower than tilapia.

Like goldfish, Koi are part of the carp family and are often classified as "dirty" fish. They are constant diggers, working the substrate constantly in search of a tidbit of food.  Underwater plants are not possible. By adding an aquaponic filter, it is a great way to have the best of both worlds - plants and fish!

Cichlids

The best fish for most aquariums are the various cichlids.

South American Cichlids

These are fish that reach larger sizes than standard community fish. They are often more aggressive.  They should be kept with similar fish - usually a cichlid tank.  The South American species are more suited to aquariums of 20 gallons or more - especially ones like the firemouth, festivum, severum, angelfish and such.  Consult your local pet stores for the species that are suitable and available in your area.

African Cichlids

African Cichlids are extremely popular and would be an excellent choice if they were able to be kept in a small aquarium.  They are not. If the system you are developing is 35 gallons or more, then various African cichlids like elongatus, zebra, frontosa, peacock and many others could be used.

They require quite hard water, so there will be plenty of trace elements in the water for the plants to remove. The pH is often quite high, but should not interfere with the plants' growth.  You might have to watch it more carefully to prevent a dangerous drop for the fish over time.  Acidification does occur normally as a result of the Nitrogen Cycle and a mature biological filter anyway.

Although Tilapia are cichlids, and come from Africa, they are not part of the classical African Cichlid set that come exclusively from the three great Rift Lakes (Malawi, Tanganyika and Victoria).  These fish are quite colourful and very active.  An added bonus is that they prefer to be overcrowded as in their native habitat. They will tolerate a much higher bioload in the aquarium than most other fish.  This means there will be added wastes for the aquaponics system to adsorb.

The drawback is that they are too big to be housed in a 20 gallon aquarium.  They are much too aggressive while looking for territory. You need a much larger aquarium for them be happy.

The addition of the aquaponics filter will remove the added wastes from the water.  The fish will thrive from the cleaner water as it is purified by plants. A win-win situation for the aquarist.  An added incentive for fish keepers who enjoy keeping lots of African CIchlids.

Catfish and Algae Eaters

There are other species which can also be considered, but often as part of the overall community, rather than a single species aquarium.  Catfish, such as synodontis and similar smaller to medium catfish are quite useful. Plecostomus grow quite large, depending on species and will keep the algae and wastes under control.  In this case, larger species can be selected.  They will grow and disturb the wastes captured on the bottom as they scavenge the area for food. The more wastes delivered to the plant roots, the purer the water will be for all the fish housed in the fish tank area.

Gouramis

Gouramies are a good choice for many smaller aquariums, especially the 20 gallon size highlighted throughout this book.  They can be more aggressive than guppies and tetras, especially the medium sized ones like the blue, gold and moonlight gouramies. But there are peaceful species as well.  The dwarf types are quite acceptable for many medium sized aquariums of 20 gallons and higher.  They can often get along quite comfortably with small fast fish like tetras, Rasboras and livebearers.  Their larger bodies will quickly add a lot of bioload into the aquarium. This ultimately provides plenty of nutrition for the plants, while allowing the smaller more common community fish to be housed as well.

Barbs

Barbs are quite active, and can grow significantly larger than many small aquarium fish.  Just be aware that they need schools of fish to be happy. If you want to keep a standard community, cherry barbs, rosy barbs and gold barbs all could be considered - the more aggressive tiger barb is an excellent choice for more belligerent tanks.  They are not so good for peaceful tanks where longer fins are featured.

Aquarium Communities

As mentioned at the outset, most aquarium communities can support the growth of vegetables and herbs in your indoor garden.  Smaller fish may not produce as much waste as the deeper bodied fish mentioned specifically.  However, wastes will be manufactured by all fish and immediately become available for the growth of plants.

As you can see, the range of fish that can be used to facilitate the growth of organic vegetables and herbs in the aquaponic filter are quite diverse.  The addition of such a filter will not limit your enjoyment of the fish you keep.  But knowing which are the best to keep to encourage plant growth will help you plan to take advantage of the symbiotic relationship between plants and fish you are creating.

11. Conclusion

Many aquarists are looking for the perfect filter to help purify and cleanse the water for their prized fish.  There are quite a few standard filters on the market: outside power filters, canister filters and a variety of other designs. All are used to remove particulate wastes and control ammonia and nitrite. Some can use special media to chemically change the water characteristics.

But in all this time, there has been no way safe and efficient way to remove the final by-product of the Nitrogen Cycle - nitrate. Although it is not particularly toxic in the beginning, it simply continues to build up until it can reach dangerous levels.  Classic filters cannot remove or detoxify it. The only way to eliminate it is to do periodic partial water changes.

Heavily planted aquariums require less removal because the plants do use nitrate as a major fertilizer.  But they can run he risk or causing a drop in oxygen levels when the tank is dark.  By creating an aquaponic filter, the plants are moved outside the aquarium and produce edible vegetables and herbs.

Aquaponics uses fish to fertilize the plants. It is becoming a very popular alternative food production system.  A well designed system requires much less resources - fertilizer, land area and water.  It will easily grow popular vegetables such as lettuce, tomatoes, kale, herbs and other commercial produce.  This is done organically.  The fish provide the fertilizer and they will die if harmful chemicals are added to enhance plant growth.

This book has taken an in depth look at the ways that this technique can be adapted to a home aquarium - to create what we term an aquaponic filter.  This benefits the fish by purifying the water of nitrate and other wastes.  Simultaneously it will be growing a small crop of table ready vegetables and herbs.

By identifying all the aspects of the filter, it has been seen that this new technology can be easily made to measure as a retrofit for small to medium sized aquariums.  They can be installed onto almost any home aquarium.  Initial diagrams and parts lists are provided that can be adapted to almost any size aquarium.

12. Resources

Grow Pans

One of the best places to get a grow pan is U.S. Plastic.  They are the direct manufacturers of the pans, and quite number of other interesting plastics.  For a two foot aquarium, 20 gallons or so, you might be interested in:

http://www.usplastic.com/catalog/item.aspx?itemid=22803&catid=852

Net Pots

One of our favourite places to look for a wide assortment of special Aquaponics products is here.

Search for Net Pots.  The 2`pots are perfect for the system we are developing on the previous pages.

Bioload Calculator

Here is a Bio-load calculator that can give some general guidelines.

Aqadvisor at aqadvisor.com

We don't trust it implicitly, and there are so many possible combinations that it may not always be perfectly accurate.  Use it, but be sure to rely on the expertise of the specialists at local live fish store to help decide the best final mix for your aquarium and plants.

For further information on Freshwater Tropical Fish visit our Website at:

Freshwater Tropical Fish Tanks

Other books by Steve Pond:

The 7 Best Beginning Tropical Fish Species For Starting A New Aquarium

Table of Contents

1. Introduction

2. Understanding Nitrate

3. What aquarists need to know about soil-less indoor gardening

4. Aquaponic Filtration

5. Aquaponic solutions for the aquarist - Bringing it all together in the home

6. Meeting the requirements of Freshwater Tropical Fish

7. Growing Organic Plants in the Filter

8. Parts to build your own system

9. A DIY Aquaponics filter

10. Fish to consider

11. Conclusion

12. Resources