The most popular fish for aquaponics tend to be tilapia, blue catfish, and goldfish. Though it is my plan to transition to tilapia, up till now, we did not have a greenhouse designed to keep them warm enough through winter. I hope that will change with the new greenhouse we are planning to build. The big advantages of tilapia is that they eat almost anything, grow very quickly, are very hardy if the water is warm enough, taste very good, and reproduce easily in captivity. The big disadvantage with tilapia is that they die when the water temperature dips below 60 degrees and really need to be in the seventies at least, to be healthy. Without a well designed system, they cost a fortune to keep alive over winter and are not really practical outdoors in a temperate climate.
I attempted to raise blue catfish the first time I tried aquaponics. Just as they were ready for harvest, my family and I went away for two days mid summer. And mid afternoon (during the heat of the day) on both of those days, the power company decided to work on nearby power lines and turned off the power. When we got back, the catfish were ready for the compost pile. It was extremely disappointing, to say the least. The big advantages with blue catfish is that are readily available and taste good. And they are hardier than some other common cold water fish (bass, perch, etc). The big disadvantages with blue catfish is that they are not as hardy as tilapia and cannot reproduce in captivity. They are primarily carnivorous, and that limits what can be fed to them if you are not feeding commercial pelleted fish food.
Goldfish, are well…goldfish. They may provide the waste necessary to support an aquaponics system and they are extremely hardy (a good beginner fish) but they are not normally eaten by people. And half the fun of aquaponics is raising fish that can be eaten.
There is another alternative very rarely considered by aquaponics enthusiasts because it is considered a “trash fish” in this country. And it is bullhead catfish. Bullheads do not get as big as blue catfish. That is one reason they are unpopular. And they can taste mucky if they are raised in mucky water. But they have some advantages that should make them worth considering for the purpose of aquaponics.
- They can taste very good if raised in clean water (better harvested when the water is cold, though, for firmer flesh).
- They are common in the US and can be easily caught from the wild.
- They are extremely hardy, as hardy as goldfish, and hardier than even tilapia.
- They grow quickly the first couple of years then slow down. They should be harvested at this point anyway, because they become more aggressive towards one another in their third year of life.
- They can reproduce in captivity.
- They are omnivores and eat almost anything (like tilapia).
Bullhead catfish eggs.
Baby bullhead catfish fry.
What I have learned about bullhead catfish:
- They are most likely to breed at two years old. They become aggressive at this age and need to be separated, a few per container. Any two year old fish not intended for breeding should be harvested at this time. They start killing each other otherwise as they become more territorial.
- They like to lay their eggs in sand or muck on the bottom. They did fine separated into horse troughs with some sand on the bottom, sunken plastic pots for shelter and aerator stones. We did not have an aquaponics system set up for these tanks and I would use a bucket to scoop out water occasionally for the garden and refill as necessary with water from the well. With only a few fish per container, water quality wasn’t a big issue.
- If there is a water pump, it would require a fine screen so that the baby fish would not be sucked up. They alternate between feeding on the bottom of the tank and surfacing to feed for algae on the sides of the tank.
- Bullhead do better in shallower tanks verses tall ones. They can handle periods of no aeration or water purification as long as the water is not too deep and they are not too heavily stocked. They are a very practical choice for a solar system not using a battery for overnight pumping.
Overall, we were very pleased with our experience of using bullhead catfish. I am excited about the prospect of raising tilapia. But for cold water aquaponics, where sustainability is important (not needing to regularly purchase new fish). bullheads proved to be a very good choice.