What is Aquaponics?

Aquaponics is the combination of Aquaculture and Hydroponics with both halves of the system reliant on each other for its success. The beauty of aquaponics is it creates somewhat of an ecosystem, in which both the fish and plants thrive. It uses a fraction of the water to grow vegetables compared to conventional soil gardening, and as the plants extract the excess nutrients, once the system is stabilised, the need for large water changes is diminished, if not eradicated, and the only water use is top ups to replace water from evaporation and transpiration.

We firmly believe in the concept of eliminating food miles, as a way of preserving our environment. There is nothing more rewarding than serving fresh fish and vegies that you have grown yourself with minimal inputs and environmental impact. A system can vary greatly in its complexity and what it can produce. Smaller systems (eg  backyard  systems) generally consists of a fish tank and growbeds filled with an inert medium (eg gravel, clay balls, etc).   The fish produce waste which is pumped into the growbeds. The grow beds have a number of functions. The medium acts as a home for nitrifying bacteria which convert the toxic ammonia to less toxic nitrite, and finally to nitrate. The plants in the growbeds, extract the nutrients and convert them to a more useful product; food. The medium also acts as a solids filter. We don’t remove any solids from the system, as compared to conventional aquaculture, we actually require the solids to break down in the system and provide nutrients and trace elements for the plants. The water returns to the fish tank for the cycle to start all over again.

Larger systems, such as commercial systems are generally much more complex. Most commercial systems only utilise the waste excreted through the fish’s gills directly into the water. All the solid wastes are removed as quickly as possible.  Instead of a medium filled growbed that traps the solid wastes, the water is mechanically filtered to remove the solids. These solids are discarded, in our case onto olive trees.  This allows more fish to be stocked into the same amount of water. The downside however is that nutrients necessary for flowering and fruiting that normally come from the solid fish wastes are lost, and hence only the leafy plants (lettuces, asian greens, herbs, silverbeet, etc) are recommended to be grown.  The plants are generally grown without the use of a growing medium, or only enough to support their roots in small net pots.

Commonly used techniques are NFT and DWC. NFT stands for Nutrient Film Technique and was originally (and still is) a hydroponic method of growing. This method of growing uses channels with holes in the top. The plants are placed in the holes and the fish waste water is flowed slowly down the channels (in a “nutrient film”) where the plants uptake all the water and nutrients they need. DWC stands for Deep Water Culture, and is also a technique first used in the hydroponics industry. Here the roots of the plants are suspended into the nutrient rich well aerated water. One way of doing this is by having the plants floating in foam rafts in large troughs.
Due to larger systems not utilising the growing medium as the biological filtration medium , additional biological filters are needed. This increases the cost and complexity of setting up a commercial system.   

In both types of systems fish food and occasionally trace elements (eg chealated iron) needed by the plants, are imputed into the system and fresh fish and plants are produced.

For more pictures of aquaponically grown plants and fish as well as aquaponics systems, visit our Photo Gallery

"The Fish Farm's" Gravel Aquaponics System

Our System is contained in a 9m by 5.4 m greenhouse with a shed to be attached to the end for the tank and sump.

We are using a 5000L composite fiberglass aquaculture tank, and an approximate 6000L sump. We dug the sump using a mattock to break up the ground and the loose dirt was scraped out with a front end loader. This was then lined with 1mm thick edpm liner. The liner is an amazing product. It comes with a 25 year warranty, and we can see why. There is no way you can tear it without the assistance of a knife or scissors. It also is food grade, which is very important. As the system is a closed loop, we don’t want any toxic chemicals building up in the water.

The growbeds are ex abalone tanks, they hold a little over 2000 liters of gravel at 40cm deep. We are more than happy to incorporate recycled materials into the systems. In addition to these four beds, we have included four 9 meter lengths of NFT channels (Nutrient Film Technique, explained in more detail above)

There is one pump in the sump which pumps to the fish tank which overflows with the use of “gravity siphon overflows” to the growbeds, and a second low wattage pump which continuously flows water thru the NFT channels.

There was the remains of a greenhouse on the chosen site but it was installed poorly so we lifted all the posts , extended the width from 4m to 5.4 by stretching out the hoops and bending straight sections at the end so the hoops slot straight into the top of the posts and made new frames out of galvanised steel. We also increased the height of the sides so instead of the hoops starting at 30 cm off the ground they start at about 1.5metres. The bottom 1.5m on the sides are shade cloth. This will give us some ventilation as the greenhouse is in full sun. The plants transpiring creates quite a moist environment, so ventilation is critical to prevent fungus and mildew.

We hosted a workshop on the 28th of October 2007 which went well, despite the fact that we were rained out at lunch time (even had some hail). On the day we got the tank in place (with about 100 large goldfish in it), the sump finished, the beds all in place and full, and trenches dug with 90% of the drain plumbing done. It turned out one of the visitors was a plumber, so he was put to work. The other visitors worked really well, dug flat spots, trenches, helped all over, with the special guest being our mate who owns the Front End Loader who moved the 12 tonnes of gravel into the growbeds for us. We had a great time and hope all who came enjoyed themselves and learnt something in the process (thanks All!!) We have future workshops planned so keep your eyes on this page!

Since the workshop, we have completed all the plumbing, and have stretched the plastic over the greenhouse hoops. We have planted out all of the beds and some of the NFT channels with various plants. (Including tomatoes, strawberries, lettuces, basil, zucchinis etc). The cherry tomatoes have been yielding very well with a continuous stream of nice round fruit being produced. Various other things have been harvested, including zucchinis, lettuces, silverbeet, lots of watercress, basil, beans, etc.

"The Fish Farm's" NFT Aquaponics system

Our NFT system is enclosed in an approx 12 by 24 meter shed. One side of the shed has clear polycarbonate roofing above three lots of NFT channels, for a total of 204m of channels.  It has a large divider down the centre of the shed which reflects the light coming through the roof back onto the plants, and off of the fish. The “fish” side of the shed consists of 7 two thousand litre tanks. These tanks are plumbed up into two modules, one of four tanks and the other of three. Each module has the tanks draining into swirl separator s which concentrate the solid wastes for easy removal. The water is pumped out of the tanks into a biological filter, before returning to the tanks.  One module can be separated from the other, for fry rearing/new fish quarantine, etc or they can be run as one larger system. Some of the filtered water is diverted through additional filters (120micron inline screen and disk filters) and into one end of the NFT channels. The water flows down the length of the channels allowing the plants to uptake the nutrients and water needed. The water then drains out of the other end and into a 1000L sump. The water is pumped from the sump back into the swirl separator on the main system.

As the solids are removed the leafy greens work the best in this sort of system.  We are growing a variety of lettuces, basil and silver beet as you can see in the pictures.

For more information about aquaponics feel free to visit the best forum in the world discussing all things Aquaponics.