Aquaponics is a framing method that relies on natural processes. An ecosystem is created where fish, plants, bacteria and other micro organisms thrive together. The fish waste is broken down by bacteria to form nutrient rich water for the plants. The bacteria and plants consume elements that would have been harmful to the fish, thus filtering the water. The result is a very low maintenance system where nature does a lot of the work with the added benefit of high throughput and yields. If installed within a protected environment like a greenhouse, one can grow produce all year round. The following diagram describes the process and the relationship between the elements:
This concept makes aquaponics fun and addictive for some, but most importantly it brings about many benefits:
- Water is circulated and never replaced. Only the water taken up by the plants and water lost to evaporation is topped up.
- Cost effective - because the system runs itself to a large extent, very little labor is required.
- If run correctly, the yield throughput can be much higher than traditional farming methods.
- One is forced to take an organic approach, as any harmful chemicals added to the system, will kill the fish.
- Multiple crops can be grown at the same time and can be changed in an instant allowing one to adapt quickly to market demands.
- Lower disease probabilities.
Like with anything in life, aquaponics is not the "silver bullet" of farming and also has some disadvantages:
- High upfront capital costs - even DIY does not make it better as this often comes with the cost of expensive mistakes (unless you build from our designs)
- It is not immune to pests, but there are methods like mixing in plants that deter pests, use of organic pesticides, beneficial insects, enclosed environment, insect tape and more to prevent and fight pests.
- Although a system can run well only with the nutrients form the fish, additional nutrients that do not occur naturally in an aquaponics system need to be added. These are iron, calcium and potassium and luckily it comes in organic forms. Another way ensure these nutrients are present is to introduce compost tea. A good practice to run in parallel with aquaponics, is to learn how to make good compost as there are plant and fish waste from the aquaponics system that can be added to organic household and garden waste to form great compost and compost tea.
Components of an aquaponics system:
- Fish tank
- Mechanical filter - radial flow filter or swirl filter to separate fish waste solids that were not decomposed.
- Biofilter - a tank with media in it that creates a lot of surface area for the good bacteria to thrive in and break down the waste. Not required if system has media grow beds (media grow beds also double up as a biofilter)
- Mineralisation tank - a mineralisation tank is used to break down the fish waste that settles at the bottom of the mechanical filter. The waste is periodically pumped (using gravity) from the mechanical filter to the mineralisation tank. The water and waste in the mineralisation tank is aerated and molasses is added to create the perfect environment for more bacteria to thrive and break the fish waste down. This nutrient rich mixture is then returned to the system after a couple of days. This is the only manual component in the system. The alternative is to dump the sludge at the bottom of the tank into containers and working it into your garden.
- Sump - a central collection point for all the water.
- Water pump - to pump water from the sump to the rest of the system. Small systems do not have to have a sump and water can be pumped from the fish tanks to the grow beds.
- Air pump - delivers extra oxygen to the fish tanks, the deep water culture beds and the biofilter.
- Deep water culture grow beds - grow beds that only contain water with a continuous flow in and out of the bed. Plants are grown on floating raft beds and their roots hang in the water. Most leafy greens are happy to always have their feet wet.
- Media grow beds - grow beds filled with gravel or leca (lightweight expanded clay aggregate). The water flows through these beds on an ebb and flow/flood and drain basis. These are for plants that do not prefer too much water and these grow beds are mostly used for fruiting plants. The cavities between the gravel or leca ensures that water reaches everywhere and also drains effectively.
- NFT (Nutrient Film Technique) systems - these normally come in the form of pipes or gutters in which the nutrient rich water flows. Plants are inserted in holes on the top of these pipes/gutters and the water flows over the roots. They come in a vertical or horizontal configuration.
- Wicking beds - these are not connected to the system and does not have a continuous water flow. They have a watering pipe that runs down the side and along the bottom of the grow bed. A layer of vermiculite lies in the bottom of the grow bed followed by soil filled to the top. The pipe has holes to deliver water to the vermiculite chamber.Water 'wicks" up from the bottom to water and feed the plants. This method saves a lot of water as it is not lost to evaporation on the surface of the soil. It is also less labor intensive. These beds are better suited for root vegetables like potatoes, carrots, onions etc. as they require more dense media than what is offered in the ebb and flow media beds. In our systems, we connect a pipe with a tap to deliver water from the aquaponics system on an ad-hoc/as required basis.
Not all the above components are required to construct a basic aquaponics system. A very basic system only needs a fish tank, grow beds and a water pump, but will not be as effective as a more holistic system.
So how much labor/time does a system require?
Altough the fish, water pump and gravity does most of the work, the following tasks are a must:
- Feeding the fish, but auto feeders are available
- Testing the water regularly and adjusting pH (This becomes less of an issue with mature systems)
- Tending to the mineralisation tank if one is installed
- Adding iron, calcium and potassium once a week or as required
Apart from harvesting, a commercial system of 300m2 only requires about 30 min of labor per day.