I just started a small, 10 gal aquarium with couple of bluegill and a small channel catfish. The problem is, that I never had aquarium before and there is more to it than just putting all the ingredients in a container and turning on the aeration and filters. (that stuff is relatively loud and my vife kicked me and my aquarium out to the garage) The water has to age, establish altae and some other stuff and it is common that the first inhabitants die. People get guppies as the first sacrifitial fish. But you may know all that already.
I am guessing that 75 gal is probably minimum if you want to observe natural behavior. They readily take to the aquarium fish feed, but I feed them mostly the same food that I put in the feeder in my pond. I crush it up a little for the fathead minnows. They eat the food OK, but you should see what they do when I catch little minnows in the ditch outside and throw them in. They twitch a little from the change in water chemistry and temperature, but not for long. They get brutally attacked and gulped down. Friend of mine had a pet Bass and he even jumped out to eat minnows and crickets from his hand. Keep a cover on, they like to jump out of the aquarium. I would really like to see them spawn.
In the end, my main purpose for starting an aquarium is to keep my Tilapia alive in the winter.
