NANFA is definitely a great resource if you are looking at raising fish in an aquarium. They also provide grants for native fish research and other good causes. They are fish squeezers much like us but in an often VERY different way... Their publication American Currents is very interesting.

I have been able to get redears pellet trained in an aquarium, much in the same way you can pellet train bass or perch. You start by feeding them live foods such as wax worms, meal worms, peices of night crawlers and feeder fish. As the fish come to learn that your presence means dinner time, you'll see them get rather animated and waiting for you to drop food in. At this point I will start to switch from live food over to freeze dried(easier and cheaper to obtain) food. Usually just a couple weeks of them being used to feeding on this food is all it takes. The harder crunchier consistency gets them ready for pellets. At that point you can toss pellets in the the fish literally blindly strike at it. After all, everything you've thrown in before has been tasty food. Most fish figure this out quickly and can bee pellet trained in just a few weeks. Some like crappies are very difficult to pellet train while pickerel are impossible IME...

The misconception that fish grow to in size to the proportions of their aquarium home is false! Usually the biggest challenge with most pond fish is they just get too darn big... Even when caught as small fingerlings, a single warm months growing season in an aquarium and they are often way too large for all but the largest of aquariums. My 125 gallon aquarium is at its max by September and that is when I usually free the occupants into a backyard "goldfish" pond if I wish to keep them or depending on the species, they may find a home in a larger pond I manage.

Sunfish are territorial buggers and will beat the snot out of each other if kept in cramped conditions. One adult fish per 10-20 gallons is a sure fire way to keep them happy. That and a lot of large rocks and drift wood for them to take cover in... They'll set up territories after some squabbling and then you usually have little issue unless new fish are added, ones are taken out or if you're lucky they get to spawning in your aquarium.

Greenies are some of the meaner ones, redbreast seem to be more docile. Rock bass are also friendly fellows but have large mouths and know how to use them. I currently have a green sunfish I rescued from a feeder fish tank at the Petco by my house. He is very well behaved, I think because he realized I saved his butt from the stomach of a large and mean tropical beast! That and he is probably a she as females tend to be better behaved but not as colorful.

Better aquarium species for those not interested in large tanks are those which don't grow to massive sizes. In place of bluegill or green sunfish species like the redspotted sunfish, orangespotted sunfish, bluespotted sunfish, black banded sunfish or banded sunfish make good candidates. The snail bullhead is a good option to replace CC or larger bullhead species. Redfin and grass pickerel reach a maximum size of a foot and make good aquarium candidates. Fliers look much like miniature crappies but only reach 8" or so. Any of the less common southern bass like the Suwannee or Redeye bass are perfect for aquariums as well...