The first time we got catfish fingerlings, they were really advanced (large) fish. Most of them had been over 6 inches long when we got them. The second time we got fish, they were much smaller as can be seen in the above picture. These are channel catfish in the 3-5 inch range added into a relatively newly set up “aquarium quarantine aquaponics system”. While they are this small, channel catfish can do ok for a while in a smaller tank. Once they get beyond about 7 inches or so, I recommend moving the channel catfish into their grow out tank of at least 300 gallons. (I’ve heard of people growing out catfish in smaller tanks but I have never had very good luck with it.)
Those little guys in that picture can grow quite fast when the water warms up and by December of the next year can weigh in between 2 and 6 pounds in our Aquaponics Systems.
If one needs to quarantine channel catfish for a while before putting them in with the general population. I would suggest having at least a 100 gallon tank tied in with at least a 100 gallon grow bed that can be kept tied in with the main system normally but when it is time to get new fish, isolate the fingerling tank with it’s own grow bed, get small fish and don’t over load the isolation wing. Then hopefully by the time the quarantine period is up, the main fish tank is ready to accept it’s new occupants. I have kept about 10 small channel catfish in a 100 gallon tank before but they didn’t do as well as fish the same age in a 300 gallon tank. I notice more stress issues and skin conditions in fish kept in the smaller tank even when the ratio of fish and tank and grow bed is otherwise exactly the same. Once the channel catfish get past about 6-7 inches they just don’t do as well in a small tank.
This is why my personal recommendation for a minimum size Main Aquaponics System fish tank is 300 gallons. It is all about my chosen fish, the channel catfish. 300 gallons makes a nice size fish tank for maintaining water temperatures as well and multiples of three are pretty nice to work with.