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.
SOME INTERESTING FACTS
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.
NUTRIENT LOAD IN FOODS
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.
WHY IS THE FLOOD AND DRAIN SYSTEM SO EFFECTIVE FOR PLANT GROWING?
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.
THE RATIO BETWEEN PLANTS CROPS AND FISH
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.
Aquaponics is the production of plant crops utilizing
the waste water and organic matter derived from the
production of aquatic animals.
Since the beginning of time farmers have used
the manure from farm animals to fertilize their
crops. Aquaponics does the same thing only
with a twist.
Global Aquatics was one of the early pioneers developing the first systems in 1986 to turn fish waste into
(Click on the picture for a larger view)
We have a lot of other prepared materials about fish farming and aquaponics, including some spread sheets, to share
with you at no cost. Just send an e-mail, call or text and ask for more information.
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.