I have a 1000 gallon koi pond in my backyard that I have some green sunfish and a bass in along with a number of koi and goldfish. I caught the bass (with a net) in a private pond when he was about 2 inches long. I put him in a 30 gallon tank and later a 150 gallon tank to grow him out so my green sunfish wouldn't eat him. Once you get the bass eating koi food he will grow about an inch every other month for the first year (and more if you keep your water warm). once they reach about 12" long they slow down on the growth. In my opinion, if you want to keep a native fish, sunfish are the way to go. They require less space, more likely to take koi food, and are more active in a aquarium setting. If you do keep a bass, I've found they do better if you get them when they are really small. make sure you find out what the laws are in your area about keeping native fish. The worst thing you can do is release a fish in a lake once its been in captivity, that is how diseases are spread. Anyways, here are some pics, these are older, I don't have any recent once of the bass but he is about 11-12 inches now. I've had some form of native fish in a tank or pond for the last 15 years so hit me up if you have any questions.