We are now moving into the more advanced and challenging ways of growing your own food. The more effort you put in up front in setting up your home garden, the more it will return you in the long term and this is definitely the case with Aquaponics. The purpose of this section is to introduce you to the aquapoincs systems available to enable you to get started researching and designing your own system.
- No weeding and digging required in Aquaponics system
- Faster and more productive growth than traditional growing methods
- Plants can be spaced much closer together (up to twice as dense) than planting in soil
- Minimal water usage – much less than the wicking worm bed method
- Added benefit of growing your own fish as well as vegetables
- Aquaponics is Organic
- One the system is fully cycled, the pH is easier to maintain
Disadvantages: More complicated process as you are dealing with live fish and more work is required up front. Higher set up cost than other methods, although you can use plenty of recycled material to help reduce this. Regular maintenance and ongoing running costs required (feeding the fish, pump operation and maintenance and monitoring the system for correct balance).
Aquaponics is a combination of both aquaculture and hydroponics. Aquaculture is essentially the farming of fish life. Hydroponics is simply growing plants in a medium other that soil with added nutrients – in this case the nutrients come from the fish waste.
The best way to describe aquaponics is a symbiotic cultivation of plants and fish in a recirculating mini ecosystem. The waste from the fish provides the food and nutrients to the growing plants and the plants filter the water as it is recirculated through the grow beds back into the fish tank.
Beneficial bacteria is what makes the entire aquaponics system work and the system is usually stable after about a month of operation. One form of bacteria converts the ammonia waste from the fish into nitrites and then another form converts the nitrites into nitrates. The nitrates then provide food for the plants, without affecting the fish. The other essential ingredient needed for the aquaponics system and all the other growing methods described are worms. The worm’s food source is the solid fish waste, which they convert into worm castings, helping to supply essential nutrients to the plants.
Choosing a location and marking out a space
Aquaponics systems can be set up pretty much anywhere that the space is available. Depending on the type of system you plan to set up, make sure you allow for the differing height requirements and that the site is level and has good access to sunlight.
Different types of aquaponics systems
Flood and drain
This the most common method amongst backyard aquaponics systems because it is the simplest of all methods to operate. The system uses a container filled with rocks or perlite for growing the plants and bacteria and housing the worms. The container is filled with water combined with fish waste from the fish tank via a pump (immersed in the fish tank). It is then drained back into the sump or fish tank by either using a bell siphon device or other flush mechanism. This process is repeated to keep the system cycling, filtering the water and providing nutrients and water to the plants
The two typical ways to flood and drain the grow beds is via an electronic timer and also a mechanical bell siphon (auto siphon) device.
Electronic timer – stand pipe
A pipe known as a stand pipe is inserted vertically into the grow bed and the height is set to the maximum water level in the grow bed. This pipe also acts as the drain pipe back into the tank. When the pump is switched off, water drains from the grow bed into the sump or fish tank through small holes that are drilled in the base of the standpipe. The pump is then switched back on once the bed has been fully drained – and the filling process begins again.
In the case where you want the grown bed continually flooded, the stand pipe will not have any holes drilled in the base of the pipe. The system will still need to constantly cycle in this case to keep the fish water moving through the media in the grow bed.
Autosiphon device – Bell siphon
The advantage of this system is that it is mechanical (does not required an additional power source to operate). The disadvantage of this system is that it is mechanical! (relies on a constant slow flow of water into the grow bed to trigger the siphon and can sometimes be a little tricky to set up for consistent operation).
When the level of the water fills to a determined depth in the grow bed, the change in pressure triggers the bell siphon to drain the water in the bed down to the base of the siphon device and the process of filling is repeated.
Here is a picture of a typical bell syphon for an aquaponics system made out of PVC pipe
This version of aquaponics system is similar in concept to how the floating raft system operates, where a separate tank has water continuously pumped through this tank, draining back into the fish tank. The only difference is that the separate grow bed is filled with a media such as rock or perlite to grow the plants. To ensure an even spread of watering for all the plants, it is recommended to set up a pipe grid on the top surface of the grow bed so the water moves through the whole bed rather than a small section.
Using a floating raft system
As the name indicates – a raft aquaponics system is typically a floatation device such as Styrofoam board with holes cut out for the plants/pots and this floats on top of the water. This water tank is usually separate to the fish tank and the water is continually pumped from the fish tank through this growing tank providing the nutrients to the plants as the bacteria living on the raft breaks down the fish waste. Note that no worms are used with this system.
Nutrient Film Technique (NFT)
This is the same setup as a hydroponics system, where long custom made channels or PVC tubing with cut outs is used to house the plants. Plants can be inserted into pots that are filled with a media such as perlite and then inserted into the main channel or pipe to immerse them in the water. Water is continuously pumped through the channels/pipe and plant roots then back into the fish tank. Because there is minimal surface area for the bacteria to grow, a bio filter is usually integrated into the aquaponics system to aid in bacteria growth.
Which system is best for you?
The concepts shown are just a few of the many ways an aquaponics system can be built and operated. There are many other design based off these concepts that work just as well. So be creative and experiment when designing your own system to see what works best for you and your backyard. The main thing to keep in mind when designing and building your own aquaponics system is to make sure the water is constantly aerated to keep the fish healthy. Also make sure the system is cycled frequently which will aid th aeration process. A good idea is to use air pumps in fish tanks of your aquaponics systems with a battery backup to prevent the fish from dying when the power cuts out.
It is also worth keeping in mind that if the power does fail, where the water then ends up? Ideally it will default to draining all the water back to the sump or fish tank, so you need to make sure your sump tank has enough capacity to hold the water in the grow beds.
This is extremely important for both fish and plant health. It is essential to have a pH testing kit as part of your system, so you can monitor levels on a regular basis and adjust accordingly. Remember the optimum growing conditions for vegetables is slightly below neutral (7).
Keep the fish well fed, but do not overfeed them to avoid build-up of ammonia. Continue to monitor pH, ammonia, nitrate and nitrite levels within your aquaponics system to quickly react to changing conditions before the fish and plants are affected. This is very important in the first few months of running your system as the bacteria start to establish.
If the water pump is immersed in the fish tank, it will require a clean out every now and then, from all the fish waste build up.
Remember – as with most gardening start with a simple system and once successful, try something a little bigger.