Learning about Aquaponics

Client James Leger Akron Ohio


Small aquaponics greenhouse

Aquaponics is the production of plant crops utilizing the waste water and organic matter derived from the production of aquatic animals.

Burdette Industries was one of the first to develop the techniques of aquaponics back in 1982. Since that time we have refined our fish growing systems to be fully compatible with aquaponics and allow you to produce the highest yields per square foot of greenhouse space possible. Our patented digester/composter technology, explained below, guarantees your crops will receive the highest value organic plant nutrient with yields as high as 25 pounds of fresh vegetables per year for each pound of fish you grow.

In a fish culture system we have waste in two forms. First we have discharged water. This water in itself already contains a lot of nutrients and small solid particulate. The other form of waste is solid matter. Either of these two turned loose in a river or lake will cause a problem. They can be sprayed on a field and they will break down much faster than normal farm animal manure because of the fact that it is already very wet and there are bacteria working on it when discharged. However, this is still not the final form for plant food. It still must go through this process.

After considering how nature works and recognizing the time involved for complete break down of the solid matter we determined that what we needed to separate the solids long before they got to the aquaponics. We then built a massive clarifier prior to the plant growing area that would allow for the solids to filter out before they got to the gravel bed. (See S-92 filtration) The effluent would now pass through the clarifier’s, then through the plant beds and then back to the fish system. After operating this system for several months we did find that we were able to keep the gravel beds from clogging but the down side was, we had to clean the clarifier’s every three or four days.This took a lot of time and effort and now we had another problem, what to do with all of this solid waste. Wasn’t the purpose of all of this to get rid of the fish waste by having the plants eat it? Within a month we found there were other problems with this new system. While the gravel plant media was staying clean, the media and the plant roots were a poor bio-filter. We were still getting too much ammonia and nitrites back to the fish tanks and the plants were being stressed from this as well. We also found another issue that concerns me to this day when people use this method. We found several bacteria, including e-coli, in the growing beds. What made this such a concern to me was the fact that I did not want e-coli in my fish tanks and I also recognized that if someone were put their hand in the gravel media before picking a tomato there would be a good chance the tomato would be contaminated with the bacteria. After a discussion with several knowledgeable folks at the University of Delaware they stated that this should not be unexpected since this would be prevalent in any septic tank where solid animal waste was being broken down and the gravel media beds were acting just like a septic tank in that they were capturing enough solid waste to encourage the present of these bacteria. When we inquired as to how to deal with this we were told that one method would be to break the solids down with both anaerobic and aerobic digestion, just like they do in a municipal waste water facility, before the waste was used for plant crops or returned to the system. They were also uneasy with returning the water to the fish system in the first place. Their analogy was, if you were to somehow treat the waste in your septic tank in a primitive manner and then return it to be used in your house you would be in jeopardy. Since no animal can do well living in his own waste, why would you expect a fish to be any different? Now it was back to the drawing board. We knew two things after all of these trials. We needed to completely remove the fish waste from the fish system in a positive manner and never bring this back to the fish system once any of it was removed. We needed to clean the water of all ammonia and nitrites. This was easily done with solids filtration and bio-filtration. We also knew from the trials that the fish waste made great fertilizer when properly prepared. There was only on solution. It would require two recirculating systems. One for the fish and the other for the plants. The follow up research would treat each one as its own entity.Building better fish filtering system has always been the main focus at our research facility, so nothing would change there. Developing a method to utilize the waste from these fish would be a new focus. Drawing on the science of treating waste in a tertiary, or three stage process like used in waste water treatment, we designed a small, inexpensive unit that could be build from common materials found in the construction industry. In our system we call this the digester.  All of the waste from the fish system goes here. Once it enters this point it is never allowed to go back to the fish system, The digester, using aerobic (ambient air) and anaerobic digestion will break the solids down to a clear liquid nutrient in a matter of days. From here the pure nutrient is circulated to the plant beds and back to the digester using a flood and drain method. At Global Aquatics we have incorporated in all of our S-series fish systems devises to totally digest the solids by means of an aerobic digester vessel and then coupled that to special plants production trays. The nutrients are then delivered to plants by a timered pump. Unlike Hydro-ponics, our plants are not growing in standing water, but rather in porous media which traps the nutrients around the plant roots.


Global Aquatics developed the first true commercial aquaponics system in 1986 as a part of an experiment in conjunction with the Food and Economic Department at the University of Delaware. The original scope of the experiment had nothing to do with what we know today as aquaponics, but rather was an experiment to build a better biological filter to provide pollution free aquaculture discharge. The experiment started in April of 1984 and over 100 different plants were used to see which ones would work best to remove all of the nutrients from the water. By the end of 1986 we had discovered a whole new agriculture science. We had developed equipment and methods that not only consumed the nutrients, we had figured out how to grow vegetable crops that were far superior to normal hydroponics crops in both texture and taste.


While this may sound a little simplistic, the reason foods grown using organic fertilizers are so superior to those using chemical fertilizers is because it is just natures way of doing things. If an orange is suppose to be chocked full of vitamin "C" the elements to cause this to occur have to be found in the food the plant takes in. When someone is using liquid nitrogen, a very good plant fertilizer, to grow the parent plant, where are the elements needed to add the food benefit of the fruit? The answer is, it is not there. This is why hydroponic tomatoes have no flavor. In order to get the full nutrient load in any vegetable or fruit you must be able to provide all of the bases chemicals in the plant food. Nature has given us the way to achieve this by using nature animal waste and plant compost. Using this method is just a continuation of the natural recycling system.


Before I explain this I need to say, not all plants need to use this method. Some plants like lettuce do very well in aquaponics using the raft system. In the raft system a pool of water is used. The lettuce seedlings are then inserted into small holes punched in thin foam boards and the boards are floated on the water. The lettuce plant will send it’s roots into the water and get its nutrient from there. For many stalk plants such as tomatoes and peppers the flood and drain works the best. Here is why. First lets look at how Mother Nature does things. We all know the benefit of worms. Among the many things they do is they drill holes on the ground. So why is this a big deal? It is because of the way a plant root system works. First of all, the roots need water. When it rains what is the best way to get water to the root? Yep! Down the worm hole. The second thing is aeration. While the plant leaves take in carbon dioxide and expel oxygen, the roots do the opposite. They take in oxygen and put out carbon dioxide. In order for the plant roots to get oxygen it has to be able to get into the ground. In order for the carbon dioxide to leave the soil it has to have an escape path. Hence, the worm hole.When we grow plants in a loose gravel bed we can easily manipulate things to copy nature with the root system. For one thing, we all know that too much water around the roots will kill the plant. This is for several reasons. One is the root can not breath to expel the CO2 or bring in the O2. The second thing is, with even a little too much water keeping the roots real wet, the CO2 will eventually become an acid that will cause root rot. This is a problem sometimes with the drip method of feeding plants and a lot of times with those using the plants as bio filters. The gravel does two main things. First of all it is the media which holds the plant in place. The second thing is it is a place for moisture to cling to feed the plants. After the plant is set in place, the water to the trough containing the plant and gravel is turned on and fills the vessel to the top soaking all of the stones. Once this occurs the water is shut off and the water is allowed to drain out. In the Global Aquatics systems this drained water just returns to the digester to be used again during the next cycle. Once the water has been removed the empty spaces between the stones load up with fresh ambient air. The plant begins to do go through the life process. The roots are supplying the plant with the nutrient it gathers from the moist stones, they are being supplied with oxygen from the trapped air and of course they are putting CO2 into the spaces. About 12 hours later the water is once again turned on. As the water fills the voids in the stone the CO2 is flushed out and a new supply of nutrient coats the rocks. Once again the water is drained away, new oxygen comes in and the process begins all over again.


I get asked all the time how much produce will you get from one pound of fish. Although this is difficult to measure most people who have knowledge in this will give you a number of about 15 to 25 pounds of veggies per pound of fish. Of course this will vary depending on the crop. It is a safe bet that you will get more pounds of tomatoes per pound of fish waste than you will from lettuce crops. This is because a large part of the weight of a tomato comes from water content.



Burdette Industries