Living, breathing, swimming creatures that help plants grow are the core of aquaponics. The plants involved won’t make it without them. Help comes from unexpected means in aquaponics as it often does in life. In this case, the help comes from fish. Kids and adults alike are fascinated by the combination of being able to grow healthy food as well as raise fish. This article offers some tips for choosing aquaponics fish; we’ll explore three key areas of aquaponics as they relate to the fish involved. First, we’ll take a look at the role fish play in aquaponics. Then we’ll investigate the types of fish suitable for aquaponics. Finally, we’ll do some exploration into fish stocking rates.
Role of Aquaponics Fish
Fish play a vital role in the aquaponics system. It’s a strange but true fact that fish are needed primarily for the waste they dispose of after being fed. Their waste is rich in nutrients that are supplied to plants which, in turn, grow and purify the water, which returns to the tank the fish are kept in. This cycle perpetually repeats itself.
This cycle is what most impresses aquaponics beginners and experts alike. Something seemingly useless (waste) is harnessed to create something not merely very useful but also very beautiful. Not only is the waste product of fish a necessary component of aquaponics, but the potential that they can be eaten is key. It’s difficult to imagine a healthier diet combination than fresh vegetables and fish that are home grown.
Types of Aquaponics Fish
An understandable question arises regarding what particular fish to raise. It can seem like a daunting task for beginners — like picking out the best shade of paint for your house. There are seemingly endless options.
The truth is, just about any fish will work in your aquaponics system so long as they’re freshwater dwellers. That being said, you can narrow down the best ones to a manageable amount. Generally, fish accustomed to your climate zone will be your best choice.
Other important factors to consider are how prone fish are to disease, whether or not they’re able to reproduce young in a tank setting (if that’s important to you), and whether you want to eat the fish you grow. You’ll want to check and see what fish are available for purchase in your area. Some fish are simply not sold in a given area, while others are considered an invasive or nuisance species and may be illegal to possess.
Whether or not you have an interest in fish as food may dramatically alter what sort of fish you want to purchase. Some fish species make great aquaponics fish for ornamental purposes but would not be a hit at the dinner table.
Aquaponics Fish Species
African Tilapia are the most commonly used fish for aquaponics. They grow quickly, can withstand poor water quality, breed successfully in a tank, and are good tasting. One important consideration with these fish is the fact that they are accustomed to a warm climate. Heaters that keep water temperatures at a consistent and adequate level will be needed if the region they are raised in is not warm all year around.
Trout are a great fish to use if heated water is not a possibility. They do well in cold water and make for excellent table fare. Trout still require that the water does not get too cold or too hot. Colder water will cause trout, or any fish for that matter, to grow more slowly than fish constantly kept at their preferred temperature range.
Often, goldfish and koi are used by those who want ornamental fish that are bright-colored and aesthetically pleasing. Other fish commonly used for aquaponics include carp (goldfish and koi are varieties of carp), cod, trout, barramundi, largemouth bass, and catfish. All of the species listed here except koi and goldfish are considered good to excellent in taste.
Some aquaponics fish species, such as koi, are prone to jumping out of the tank. A net covering the tank will prevent any potential losses both from jumping and predators.
Aquaponic Fish Stocking Rates
Once you’ve chosen which species of fish best suits your interest, you’ll have to decide how many fish you need. No matter how large of a fish tank you’re using, over-stocking can occur. Not stocking enough fish, for obvious reasons, is not desirable either. You want the maximum yield of fish for the area you have available. Simply stocking as many fish as you can will not achieve desired results. This can result in a buildup of ammonia and nitrites in the water that can be harmful to the fish if the plants in the grow beds are not evenly matched and cannot adequately filter the water. Even in large natural bodies of water, when there are too many fish of a certain species present, those fish tend to be stunted and grow slowly.
Thankfully, there is a fairly exact science in figuring out an answer to the number of fish you should stock. A good rule of thumb is to stock 25 fish per 500 Liters of water. If you have half of that water amount then you’ll want to choose about 12 fish. These numbers are meant to give an idea of the maximum fish you can grow to eating size given the available space.
The above stocking rates are only a guide, though. Many other variables such as oxygen content, water depth, and the efficiency of the filtering system you have make these numbers vary a bit. How well or poorly the waste of the fish is filtered out of the water will be a major factor in how dense the fish will successfully thrive.
Much of the adventure and joy of this process is learning new things and becoming more skilled at a very useful science. No doubt, you will put a lot of research into the subject of fish in your aquaponics system. If you haven’t taken the step to purchase fish yet, hopefully this article helps point you in the right direction.
Now that you have a better idea of the role fish play in aquaponics, what types of fish are suitable, and the amount of fish you need; you’re ready to go! What are you waiting for?
Featured Image by Cara Harpole/Flickr