Aquaponics is a technology that offers a source of the freshest fish and organically grown vegetables. It gives everyone a chance to become a producer.
Fish are the heart and soul of an aquaponics system. They give life to the plants and food for your family (if you decide to raise fish to eat).
One of the questions most commonly asked is how many fish can I grow in my aquaponics system? I’ll touch on that topic in this article and give you a good idea of what to expect.
Aquaponic Fish Ratios
When you’re growing fish for food, you have to take into consideration the cost / benefit factor. Exactly how much money can you save on your grocery bill through aquaponics?
As a general rule of thumb for a media-based aquaponics system, for every five 20 to 40 litres of fish tank water you can expect 500g of fish.
A system that is monitored in a professional manner with a mechanically filtered aquaculture facility in place, it’s possible to stock 600g of fish for every six litres of water. However, this is most realistic for commercial facilities where performance is constantly being monitored by experts using expensive computer equipment and other technology.
Commercial systems also filter solid waste and remove it entirely from the system. Fish are also graded and separated. The bigger than average “bullies” are moved into tanks that contain other fish of similar size, while the “runts” are culled to ensure that each tank has fish of the same size for more efficient production.
In a home aquaponics system, it’s better to actually have a range of growth rates to harvest fish regularly over a long stretch of time.
Over time, an additional rule of thumb for home aquaponic gardeners has been developed. Since it’s not really convenient to consider stocking densities in terms of the fish weight, you can think about stocking your tank in terms of the number of fish.
The rule is around 1 fish for every 20 litres of water which is convenient to say the least because when your garden is first started, the biofilter which is evolved from the development of the nitrifying bacteria in the grow beds is still immature. Therefore, it can only handle a small percentage of the waste it’ll be able to deal with when it’s fully matured.
For example, say if you were to have 20 fish fingerlings to begin a newly cycled 400-litre system, the fish and bacteria biofilter will age together.
When you have just fingerlings, there won’t be much ammonia to convert to nitrates but as your fish get bigger and mature (9-12 months), they will release more waste and your biofilter will also be mature. It’ll then be able to efficiently convert the higher ammonia and solid waste load from your fish that are 500g or more.
When people first start out in aquaponics, a common mistake many of them make is that they stock more than the rule of thumb. It’s tempting but pushing these limits often leads to disasters. It’s a good idea to be well prepared with some of these useful fish care products.
Please remember that your grow bed biofilter can only process so much fish waste at any given point in its development. I recommend that you take a safety first approach that has proven to be effective. If you want to find out about what fish works well in aquaponics, then check out the Top 7 Aquaponics Fish Species article.
To get the most out of your aquaponics system, I highly recommend the following articles, where you can decide from the highest rated and bestselling products for aquaponics.