Wikipedia defines aquaponics as “a food production system that combines conventional aquaculture, (raising aquatic animals such as snails, fish, crayfish or prawns in tanks), with hydroponics (cultivating plants in water) in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity.”
In an aquaponic system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrogen-fixing bacteria into nitrates and nitrites, which are utilized by the plants as nutrients. The water is then recirculated back to the aquaculture system.
So what does this mean?
It means that your aquaponics system is supposed to be self-sustaining without you having to supplement it with nutrients. There are a few factors involved in regards to nutrients.
Firstly, you fish must be fed with high quality fish food. When they consume good food, their feces contain more nutrients. Secondly, the pH level needs to be stable. If the water is too acidic or alkaline, your system will have problems. Thirdly, the bio filter plays a large role in determining how much nutrients are available for your plants. The more mature your bio filter, the better. It will usually take about 6 months for a bio filter to properly supply all the nutrients the plants need. In the first 3 months, it would be better to cultivate plants that require fewer nutrients to grow well.
So what is a bio filter and how does it work?
For an aquaponics system, the media bed is known as the bio filter. When the fish pee, ammonia is present in the system and a process known as ‘cycling’ takes place. When there are sufficient bacteria to convert all the ammonia and nitrites in the system into nitrates, then cycling is complete. This means that your plants will have sufficient nutrients. All this takes place in the media bed and that is how a bio filter works.
Sometimes, if you notice your plants are wilting or not as luscious as they should be, it may not necessarily mean a lack of nutrients. It could be a pH value that is not ideal. You want to aim for a pH value in the range of 6.8 to 7.0. If the pH value is too high, you will need to bring it down very gradually.
Dont panic and try and bring it down too fast. Sudden fluctuations will affect the entire system negatively. Slowly bring it down by 0.2 every day till you reach the desirable range.
So now, will you need to supplement?
Well, in the initial 6 months you may wish to add some supplements, but beyond 6 months, you rarely should. There is a product on the market that is commercially available. It is known as Maxicrop and adding this to your system will help provide it with all the nutrients it lacks in the first 6 months.
There is much more to this topic that is beyond the scope of this article. You may wish to know how to lower the pH value and other matters pertaining to your system. The best way to learn would be to pick up an aquaponics guide or get an online video course. There are a few very good ones on the market that will make you an aquaponics expert in no time. Do check them out.