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A pilot project to investigate alternative hydroponic components and livestock in aquaponic systems

Based in the greenhouse of the al-Basma centre, and funded by Elsamex S.A. de C.V., we recently started a new project to investigate other possibilities for aquaponic systems. Up until now, we have been using the “flood and drain” growbed system. Flood and drain involves a growing-medium (e.g. volcanic rock) filled growbed which slowly fills with nutrient rich water, and then drains rapidly into a sump tank. Plants are planted into the growing medium as if it were soil. Flood and drain is easy to operate and conceptually easy to understand, but does have a few problems, particularly for use in very space-limited areas: suitable growing medium is heavy and expensive, and growbeds have a relatively large footprint as they can not really take advatage of vertical space.

The objectives of this experimental project are to demonstrate three further hydroponic techniques (Nutrient Film Technique (NFT), Floating Raft and Vertical Grow Towers) that can be incorporated into aquaponic sytems to increase their versatility, and to experiment with growing Australian redclaw crayfish Cherax quadricarinatus in aquaponic systems.

Nutrient Film Technique
A thin film of nutrient rich water flows along the bottom of NFT pipes. Plants are planted in baskets through holes in the top of the pipe such that their roots can reach the water. NFT pipes do not offer the same root support as a medium filled growbed, but are lightweight and can be stacked one on top of the other, creating green walls.

Floating Raft
Floating Raft growbeds are filled with aerated, slowly flowing, nutrient rich water. Styrofoam sheets are floated on the water surface, and the plants are planted in baskets through holes in the styrofoam. The plant roots are always immersed in the oxygenated, nutrient laden water. This growing technique does not offer as much root support as a medium filled growbed, and has an equivalent sized footprint. However, it could be very useful on rooftops, for example, as there is no need to transport hundreds of kilograms of growing medium. Also, the increased overall water volume compared to a similar sized flood and drain system gives increased thermal stability to the system. In addition, the aerated water under the plant roots provides a great habitat for other aquatic animals such as crayfish or freshwater mussels.

Vertical Grow Towers
Often called “strawberry towers”, as they lend themselves very well to strawberry production, vertical growing towers are very space efficient – they can be suspended right above the fish tank. Grow towers are filled with growing medium, and plants are planted through the sides. Water trickles through the towers from the top, draining out through the bottom. Due to the high surface area of growing medium within the towers, grow towers can also increase filtration in an aquaponic system.