Although the TECHNOLOGY in the field of aquaponics is well established, optimizing the mechanisms that make it work is in continuous flux. The project we are planning recognizes the early work done by Dr. James Rakocy's team at the University of the Virgin Islands. However, we will more closely follow the methodology developed by Dr. Nick Savidov's group at the Crop Diversification Center South in Brooks, Alberta. While the Rakocy model is an open-air system, which takes advantage of their climate, the "Brooks System" was developed for use within a greenhouse environment, necessitated by our temperate bioregion.

The original approach that had been used in the commercial systems developed by these researchers is described first. Then we summarize the Brooks System innovations.

Tilapia fry were introduced in succession every six weeks into one of four rearing tanks. Each tank's population was therefore at a different stage of development. As each tank was harvested it was stocked again to provide a continuous 24-week cycle. This is the period of time that it takes to raise the fish to an edible size.

The water from the fish tanks flowed into clarifier tanks to begin reducing the solids which are uneaten feed and tilapia excrement. These solids were regularly flushed out of the clarifier tanks to be utilized as field soil conditioners. The water then continued on from the clarifiers into bio-filtration (also called mineralization) tanks where solids were further reduced and the conversion of nitrogen into a form that can be used by the plants was accelerated.

The water then passed through a final tank to allow undesirable gasses to be released before it entered the hydroponic component where the plants were grown. This "raft tank" takes its name from the foam slabs that float on its surface to support the plants. The plant roots are suspended within the nutrient rich water through holes in the rafts, which facilitates lush growth. The rafts, tank walls, and plant roots provide additional surface area for further nitrogen conversion.

From here the water dropped into a sump, where pH could be controlled, and was then pumped back into the fish tanks through a water heater that maintained a constant system temperature. This sump pump was the only one in the system. All other flow to this point was by gravity.

There was also continuous aeration within the system to maintain adequate oxygen levels for fish health, and to minimize the potential for toxic anaerobic processes downstream.

Dr. Savidov's team has investigated the "secret ingredient" that allows aquaponic vegetative growth to exceed that of traditional hydroponic systems; something he called "liquid soil". Microbial (and macrobial) flora and fauna do more than nutrient cycling, they can buffer against rapid changes that might otherwise do harm. This is the same role that biodiversity would perform in the natural world.

Dr. Savidov suggests that defining aquaponics as simply the synergy of aquaculture and hydroponics overlooks this critical biodiversity. Combining hydroponics with aquaculture introduces a microbial complexity that would not exist in either system independently. These microorganisms become the catalyst, the critical component necessary for the health and productivity of the combined system. Ergo, the term "Aquaponics" is something MUCH MORE than just combining aquaculture and hydroponics. Perhaps a new term that more accurately describes the discipline is required.

Since there is already some suggestion in the literature that the study of wetlands be called Paludology (after the Latin 'Palus' for marsh), perhaps aquaponics should be called a "Recirculating Paluculture System", or RPS. This is very close to a well-recognized term in the aquaculture industry, so it's not that big of a leap. We may need to think in terms of a more science-based approach if we are going to gain broader credibility.

One of the main Brooks System innovations has been their success in closing the solids loop. Aquaponics has always been a friend of water conservation because most of it is recycled as part of its very nature. However, the flushing of the solids that accumulated in the clarification process had been a source of water loss. They have closed that loop by retaining those solids within the system in a parallel process stream. Not only is the water saved, but these solids also provide another substrate for symbiotic microorganisms to increase biodiversity within the system.

This water savings is not a trivial point, even for those of us in Alberta. In case you haven't been paying attention, not only are we losing our glaciers, which are a significant source of our freshwater resource, but climate change also means less predictability of precipitation, wind, and temperatures. The trend is towards a negative hydrological balance. The future of freshwater resources in this province, as with much of the rest of the world, may be in dire straits. Wringing every drop out of the aquaponics process will become more and more important as we move forward.

Other developments in the Brooks System include the use of a micro-screen drum filter in place of the clarifier tanks, the use of oxygenation in place of aeration, and the use of a rock bed to perform pH buffering. The drum filter is compact and operates automatically. In a commercial sized system these factors reduce capital and operating costs. The removal of aeration from the fish culture tanks reduces solids breakdown. This keeps the fish tanks clearer and makes solids removal downstream more efficient. By introducing oxygen at supersaturated levels into the raft tank, not only do the plant roots have sufficient levels for optimal growth, but the residual levels of dissolved oxygen after the water leaves the raft tank and enters the fish tanks is still well above what is possible with aeration. The other benefits of oxygenation vs. air blowers are that an oxygen concentrator uses a fraction of the power required for aeration air blowers, and humidity issues within an enclosed structure are minimized. Since the nitrogen cylcing that happens in these systems cause the overall pH to drop (become more acid) the Brooks team added a carbonate rock bed to buffer against this process.

As we can see, exciting innovation is inevitable as aquaponics research continues.

Come join us and ride the wave.

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