At its most fundamental level, aquaponics is the growing of plants in water where fish also live. There is no soil in the system. Instead, all the necessary nutrients exist in solution in the water. The fish are fed, and then excrete their waste.
Under normal circumstances, the build up of this waste would end up becoming toxic to the fish. However, in an aquaponic system, the plants growing in the water actually make use of the waste - it is a source of nutrients for them, a natural fertilizer. The fish feed the plants, and the plants purify the water for the fish. It is a win-win system.
When done correctly, aquaponics can be a highly sustainable and efficient way to produce food. Aquaponic systems are relatively easy to set up, and depending on the kind of operation you are planning to run, can be very affordable as well. The key things to consider of course are the kind of aquaponics plant and fish you want to raise. Here we take a look at different plants that thrive in aquaponic set-ups, and how you can best nurture them.
The best plants for aquaponics systems depend on how big your system is. If you're working with a small system, you'll want to go after plants that require a lower nutrient concentration, as you'll have fewer fish and so less waste to fertilize your plants with. Generally, leafy greens and herbs are great candidates for small system aquaponics plants.
Leafy lettuce is one of the most popular aquaponic plants. It is a common choice with novice farmers who are just getting started with aquaponics and don't have too much experience growing. Lettuce thrives in water temperatures between 21-23 degrees Celsius. The only decision left is to determine whether you will start your seedlings directly in the aquaponics system, or in germinating trays.
Another popular choice, watercress is a great plant to start with for beginners. It is super easy to grow, and it grows fast. Plant just one watercress plant and watch it multiply at an astounding rate. The downsides to consider are whether this rapid growth will outpace and therefore choke out your other plants, and whether you'll be able to eat and/or sell all the watercress you end up producing.
This herb is a very easy plant to grow in an aquaponic system, as it is very resilient. It can tolerate a wide range of pHs, making it insensitive to fluctuating nutrient levels. It is also considered a 'high-value crop', meaning if you're looking to sell your basil produce, you can make a pretty profit year round with aquaponics - something unthinkable in a soil system herb farm.
If you're looking to farm plants beyond greens and herbs, you might be interested in a larger scale aquaponics operation. In this case, you're able to experiment with plants that have higher nutrient requirements, as there are more fish and therefore more waste in the system. Here, it is wise to monitor nitrate and electrical conductivity levels in the water, to ensure the bioavailability of nutrients is optimal.
It is also worth noting if you decide to cultivate a mix of small and large system aquaponic plants,
Tomatoes do surprisingly well in aquaponics systems. The real benefit comes from being able to tightly control the temperature of the environment, maintaining it as close as possible to the optimum for tomato growth. However, tomatoes are known for attracting pests that can be especially challenging to get rid of in a system that doesn't allow for pesticides and other harsh chemicals, as they will mess with the fish and bacteria in the wider system.
Peppers can be a little tricky to grow in traditional soil systems. This is due to their requirements for lots of daily sunshine and how particular they are about the water they consume. However, in an aquaponics system, peppers can thrive. It is worth noting that aquaponic peppers don't do well in a DWC aquaponic system, and need a flood and drain system with a syphon instead.
Cucumbers are fantastic plants to have in your aquaponic system, they grow really nicely there. There are a few things to bear in mind with them though, making them more suited to the intermediate grower.
Firstly, their root systems can become quite extensive, so you'll need to keep an eye on them to ensure they don't get out of hand and start blocking your pipes. Secondly, they are very good at hoarding nitrogen, thereby depriving other plants of their nutrients. For this reason, it is recommended to plant cucumbers 30 - 60cm apart.
Cauliflower is a great plant for a beginner, as it is very hardy and requires little to no maintenance. Additionally, they are naturally very resistant to pests and diseases. For best results, cover the cauliflower in its own leaves to prevent exposure to direct sunlight and help it grow even bigger.
There are some plants that you should avoid if you have your heart set on growing in an aquaponic system.
Blueberries grow best in low pH environments, which are hard to maintain when you have fish cohabiting in that same water.
In contrast to blueberries, chrysanthemum does best in high pH environments, which are also hard to maintain with the fish living in the same water as the plants.
Mint poses a different challenge to aquaponic farmers. The roots of this herb grow so fast and spread so quickly, that you risk choking your whole system out if you aren't sure what you are doing.