Green Garden

Things to Consider when Choosing Aquaponic Fish

Koi are a an excellent option for those wanting  to stock ornamental aquaponic fish.

Help comes from unexpected means in aquaponics as it often does in life.  In this case, the help comes from fish. Living, breathing, swimming creatures that help plants grow are the core of an aquaponic system. The plants in your aquaponic garden won’t make it without them. Kids and adults alike are fascinated by the combination of being able to grow healthy food as well as raise fish, whether for the table or just to admire for their beauty.  In this article we’ll explore three key issues related to choosing aquaponic fish. Firstly, we’ll take a look at the role fish play in aquaponics. Secondly, we’ll investigate the best fish for aquaponics and how to choose the species that best meets your needs. Lastly, we’ll delve into aquaponic fish stocking rates.

Role of Fish in Aquaponics

Fish play a vital role in the aquaponics system. Aquaponic fish waste is rich in nutrients that are supplied to the plants, which in turn grow and purify the water, which is then returned back to the tank the fish are kept in. This cycle perpetually repeats itself.  Win-win for fish and plants.

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, free from chemical pesticides, medications or growth-stimulating hormones.  

Best Fish for Aquaponics

A common question that typically arises is ‘what are the best fish for aquaponics?’ It can seem rather a daunting choice 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 this list down substantially by taking a few things into consideration. But, generally, fish accustomed to your climate zone will be your best choice. 

Other important factors to consider are how prone the fish are to disease, whether or not they’re able to reproduce in the confines of a tank setting (if that’s important to you), and whether you want to eat the fish you grow. You’ll also want to check 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 stock. Some fish species make great aquaponics fish for ornamental purposes but would not be a hit at the dinner table.  

Types of Aquaponic Fish

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 heating the water is not an option. 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 that are constantly kept at their preferred temperature range.

For vegetarians and those who don’t fancy the idea of bumping off the fish they have tenderly raised, goldfish and koi are a good choice. These brightly-colored and aesthetically pleasing ornamental fish are readily available and very hardy. Since they are cold water fish, they are relatively easy to keep and there is no need for heaters or thermostats.

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.

Aquaponic Fish Stocking Rates

Once you’ve chosen the most suitable species of fish that best meets your requirements, 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. If the ratio of fish to plants in the grow bed is not evenly matched, the plants cannot adequately filter the water. This can result in a buildup of ammonia and nitrates in the water, which can be harmful to the fish. 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. The key is to have a balanced ecosystem that ensures the plants get sufficient nutrients without being overloaded, so that they can filter out the waste, returning clean water back into the fish tank, and thereby providing a healthy aquatic environment to allow the fish to thrive.

Thankfully, figuring out the number of fish you should stock is a fairly exact science. A good rule of thumb is to stock 25 fish per 500 Liters (132 gallons) of water. If the volume of the tank you have holds half as much water, then you’ll want to choose about 12 fish. These numbers are meant to give you an idea of the maximum number of fish you can grow to eating size given the available space.

However, the above stocking rates are only a guide. Many other variables, such as oxygen content, water depth, and the efficiency of the filtering system you have, could affect the stocking rate. How efficiently or inefficiently the fish waste is filtered out of the water will be a major factor in determining the maximum number of fish you can stock in order for them to thrive. 

Much of the adventure and joy of this process is learning new things and becoming more skilled at a very useful science — it will help feed you and your family after all. If you haven’t taken the step to purchase fish yet, hopefully this article will help to point you in the right direction.  

Featured Image by Pexels from Pixabay

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