Fish are the power house of an aquaponics system, they provide the nutrients for the plants and if your growing edible fish, then they also provide protein for yourself. Keeping fish may be a little daunting to some, especially those without any prior experience, however you shouldn’t be discouraged. Keeping fish in an aquaponic system is more simple than keeping aquarium fish, so long as you follow simple guidelines then growing fish from fingerling size, to ready to eat fish can be extremely simple.
Choosing a fish species
There are many different species of fish that can be used in an aquaponic system, depending on your local climates and available supplies. Our local climate in Perth, Western Australia, allows us to keep Rainbow Trout through winter, then a warmer species like Barramundi during summer. There are also a few choices for year round fish that we could grow, but they often take a longer time to mature. If you live in a cooler climate you might be looking at growing Trout all year round, or perhaps another locally produced fish species. In warmer areas of Australia people generally grow Barramundi, or Jade Perch year round, in most warm areas throughout the world Tilapia is the fish of choice.
In deciding what is the best species for you to grow, you should take a few factors into account, most importantly is what you want from your system. If you don’t want to eat your fish then you probably won’t want to grow edible fish, or you may want to grow an edible fish that can live year-round in your area, so that you’re not having to harvest fish out seasonally. The second most important factor is ‘What’s available?’ You need to be able to buy fish to stock your system, even with species such as Tilapia that breed readily, you need to get your broodstock in the first place.
Here’s a list of useful aquaponic species with a few details about each
Barramundi are often grown in aquaponic systems through the warmer months of the year. Most growers will buy fairly mature stock so that they can harvest larger fish, at the end of the growing season. Barramundi that is grown in an aquaponic system has an exceptionally clean, crisp taste. Growing your own Barramundi excites guests and is the envy of neighbours. They provide a decent harvest at the end of the season and are one of the more majestic species of edible fish.
There are many different species of catfish around the world that are well suited to aquaponics. Channel catfish are the most widely farmed aquaculture species in the United States, and they are available in many areas of Australia. Catfish don’t have scales so they need to be skinned, they are quick growing and have a good food conversion ratio.
There are many species of carp that could be very well suited to aquaponics, unfortunately because of their reproductive capabilities, their tough nature and ability to readily adapt in many areas of the world, carp have become noxious pests to native waterways and the environment, and as such they are not easily obtainable, and often there are high fines and fees for keeping them. In most western cultures carp also have a fairly poor reputation, as an eating fish, however, carp is still the most widely cultured fish in the world as it’s grown throughout most of Asia.
Although some people may group these with the carp, I’ve decided to cover these seperately as most people refer to them as goldfish, and this is what they will be sold as, at local pet shops or fish suppliers. Goldfish are generally pretty tough and make a great addition to an aquaponic system. In many areas they will breed in a tank, although they generally need plant cover within the tank to breed.
This native Australian fish i’s worth a special mention here, as it has the highest levels of omega three oils of any fish species in the world. In fact it’s so high in omega three oils that growers are trying to breed the oil out of them, they are trying to breed a less oily fish because they’ve found people don’t like the high oil content.
They require warm water and consume an omnivorous diet. Very well suited to an aquaponic system, they grow quickly and fingerlings are readily available in warmer areas.
Once again, another species of carp, but better known as “Koi” rather than carp. Koi are very common within many Asian communities and they are often found in large ornamental ponds. For those who love Koi, an aquaponic system is a great proposition for stocking the fish.
Murray cod are a magnificent native Australian fish, known to grow to enormous sizes in their native habitats, their tank culture is still in reasonably early days. Murray cod are grown in recirculating aquaculture systems, and can also been grown in aquaponic systems, hopefully this fish will be utilised more over time because they are quick growing, and a great eating fish. One of the downfalls is that they must be kept at high stocking densities, and kept well fed otherwise they cannibalise each other.
Silver perch are a good allround native Australian fish that grow well under a variety of conditions. Perch are omnivorous and will happily eat green scraps as well as Duckweed and Azolla. They grow within a wide temperature range, though they’re not as fast growing as many other fish, taking 12-18 months for fingerlings to grow to plate size.
The second most cultured fish in the world, and extremely popular in Aquaponics systems. They are an ideal species for aquaponics for many reasons. They are easy to breed, fast growing, withstand very poor water conditions, consume an omnivorous diet and are good eating. The only downfall for some people will be that Tilapia require warm water. If you live in a cool area you are far better off growing a fish species that will grow well in your temperature range, rather than trying to heat the water. Tilapia are also a declared pest in many areas.
Trout are a great fish for aquaponic systems where water temperatures are a little cooler. Trout prefer water temperatures between 10°C and 20°C. They have extremely fast growth rates and excellent food conversion ratios.
Numbers of Fish
This can be quite a hot topic of debate amongst people who practice aquaponics. Stocking levels of fish within a system can be as high as many intensive recirculating aquaculture systems, however the higher the stocking density the higher the likelihood of things going wrong. In very heavy stocking densities you need to keep a constant eye on all water parameters to be sure that conditions are kept at the optimum.
If you lower the stocking levels of fish then you lower your levels of risk and stress. Growth rates of plants in lightly stocked systems can still be very impressive, this eight bed system was stocked with only 70 fish, thats less than 9 fish per growbed.The fish tank is 5000L and there’s a 1000L sump on the system. The fish in the system at the time of taking this photo were trout and they were around 300 – 400g. The plant growth in the eight beds was fantastic. A wide mixture of plants were grown in the beds.