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Developing an Aquaponic System By Myles Harston My Interest in Aquaponics...
My interest in aquaculture and aquaponics started when I was a young boy. I had aquariums full of various kinds of tropical fish all over the house. My mother wanted to use dechlorinated water for our house plants and she reasoned that my aquarium water had no chlorine and that it may have some helpful nutrients. The results were unusually wonderful growth and absolutely beautiful house plants.
In the mid 80's, I began working for a fabrication company that specialized in aquacultural plastics. As I looked at the aquaculture industry, I realized that plastics and aquaculture were a natural match. One of the nice advantages we had while developing our system was the ability to quickly modify the plastic products we were working with and this helped to accelerated our research and development. We worked with several different kinds of liner material In the early stages of our Aquaculture program, a friend would bring us house plants that she seemed to kill very quickly. The first one she brought was a dried up, half dead Philadendrium. Just for the fun of it, we put it in the fish house and hung it above one of the tanks. Several times a day we would fill the pot with fish water and let the excess drip back into the tank. In less than one week we saw dramatic improvement and, in fact, the plant nearly took over the fish house! Many of the people who came to visit our facility would ask for a cutting of the monster Philadendrium because they thought it was a speacial plant. Since then, we have successfully grown a number of different house plants this way.
Developing a System...
About ten years ago we began working with Byron High School and assisted them in starting their aquaculture, and later, their aquaponics programs. Since then, Byron's Agriculture program, featuring aquaculture and aquaponics, has grown to accommodate over 400 of the 525 students in the high school.
While developing a system for aquaponics we have tried a number of different methods and configurations. Many of them work well but there are several features we feel work the best and provide the most efficient operation and lowest initial investment. The first of these is a solid, stand-alone aquaculture system that is easy to clean and maintain. An aquaculture system should be able to grow fish at close to 1/2 pound per gallon of tank water by itself. Obviously, more nutrients are produced by a heavier population of fish. However, if you do have a densely populated fish tank with your bio-filtration totally dependent on the plants, there could be major problems if something goes wrong with the plants.
The fish produce ammonia which is toxic to themselves, especially in its unionized form. Beneficial Nitrosamonas Bacteria convert ammonia to nitrates which are also toxic to fish and can cause brown blood disease. Another beneficial bacteria, Nitrobacter, then convert the nitrites to nitrates. In an aquaculture system, nitrates will continually build up, but most fish can tolerate high concentrations of nitrates. I've pushed some systems well over 300 PPM nitrates with no adverse effects to the fish. The wonderful news about fish water is that nitrates are a very available form of nitrogen to plants.
The System...
After experimenting with several different plant growing method, I realized that I like grow beds because of their simplicity and economics. A large part of the growbed can be assembled on site using local materials. As a base, plywood sheets (4' x 8' x 3/4") work well. For the sides, I use 2" x 6" lumber. Depending on available space, you can work out the exact length.
To hold the water, use a PVC liner. It is a tough material yet flexible and easy to repair, plus fittings can be glued right to it. A PVC coated mesh can be glued over the opening to the return drain to stop debris from leaving the growbed. Stands or something like saw horses can be used to hold it off the ground at a gentle angle of about 2" for every ten feet. Course perlite is a good growing medium. It is light weight and can be changed periodically. I recommend 1/2" vinyl tubing to carry the water from the fish tank to the growbed because it keeps flowing with very little clogging.
Two Designs...
We set up two different growbed designs to compare which we liked better. They both worked but each had advantages and disadvantages. In the first design, the water from the fish tank was pumped through it and it drained back into the tank. This worked very well with the advantage that it provides much more bio-filtration in the culture tank, giving the water more denitrification, degassing, and oxygenation as it goes through the growbeds and back to the tank. The disadvantage comes when you need to treat the fish or plants for disease or parasites.
In the second design, the slurry water from the tanks was pumped into a reservoir that sits below the growbeds. This slurry reservoir needs to be continually aerated because it is rich in nutrients and aerobic bacteria. Not aerating this water would result in ammonia being generated and a smelly anaerobic mess. The water is then pumped through coarse perlite and back to the reservoir. After 2-3 days, the ammonia, nitrites, nitrates, and CO2 drop and the dissolved ozygen increases at which time you can safely return the water to the fish tank. With either of these methods, virtually all of the water from our aquaculture facility can be utilized and reused.
What We've Grown...
With these growbeds we have successfully grown a number of edible plants including 4 varieties of basil, 4 varieties of leaf lettuce, chives, parsley, and swiss chard. We also had great results with about 20 different ornamental plants including marigolds, zinnias, and citronella. We had moderate success with tomatoes and worked with several other fruiting plants that grew well but did not fruit due to the lack of phosphorous and potassium in the water from our fish tanks. I believe if we had supplemented these elements the plants would have set and produced fruit.
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and settled on PVC. We have used this successfully for tank liners, ponds, raceways, ocean containers for hatching, and various other functions. We were also able to weld rigid PVC into various shapes for use throughout our system. One of our areas of emphasis was small recirculating systems which could be used by schools and small commercial growers. After many improvements in quality, our emphasis fell on keeping it simple. The Fisheries AquaRanch™ was the result.