We constructed two separate aquaponics systems: one by the name of “Nutrient Film Technique (NFT)” and the other a clay bed system. The purpose of constructing both systems is to test the efficiency of each, which, in addition to other factors, depends on the specific plants being grown (we planted leafy greens, including tomatoes and basil). In either case, it is necessary to have a large ratio of plant-growing surface area in relation to the area in which the fish are reared, in order to prevent toxic levels of ammonia rich organic matter from accumulating. Below is an outline of each system.
Clay Bed System (Sistema de Camas de Arcilla)
The clay bed system is the simpler of the two systems. It involves a large bed of clay pieces in which the plants are grown. Clay is used for its water retaining capabilities. Water can be run through the bed either continuously or in a flood-and-drain manner. Water reaches the bed from the fish tank through a sedimentator and collector, to separate out solid organic matter produced by the fish, and a reservoir from which the water is pumped. After running down the slightly sloped bed, the water is then recycled back into the fish tank.
Nutrient Film Technique (Sistema NFT)
NFT is named as such because of the small amount of water running through the pipes, creating just a thin film of water to dampen the roots rather than having the roots completely submerged. In order to create an NFT system, holes able to fit plastic cups must be cut in PVC pipes. The PVC pipes should not exceed more than about 10-15 meters in length in order to prevent nutrient depletion for the plants at the end of the pipes. Holes must also be poked in the bottom of the plastic cups to allow for the plants to access water. Then the cups should be filled with a water-retaining medium. In some cups, we used clay, and in others we used a straw-like medium. Upon evaluation of the system, the efficiency of these two media will be compared. Along with the medium, a seedling is placed in each cup, which is then placed in the plastic pipe. This completes the hydroponic portion of the system. To complete the entire aquaponics system, a fish tank must be connected to a sedimentator and collector, as in the bed system. This must then be connected to an additional filter, and then to a reservoir from which the water will be pumped out through the plant-containing pipes. As in the bed system, the water is then recycled back into the fish tank. The need for a filter in this system is due to the small volume of the system, which does not allow room for nitrogen fixating bacteria. This design is specifically beneficial to smaller plants, as larger root systems may not be contained in the small plastic cups and large plants may become too heavy for the pipes.
System blueprints:
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