We have (white) catfish in our old pond and will put white cats in the new pond once we see how it does over the summer.
You can check your local feed stores to see if they have a 'fish day'. Our store has them about 3 or 4 times a year. Also you could check your ag dept. they should be able to tell you of people in the area that sell fish. We also have an ag paper (well N.C. does) that has a fish section in it.
As for the organic fish food ... the old pond has a pretty good balanced system going on, so the only food we feed the fish would be a worm (on a hook) With the new pond, if all goes well, we would have to feed the fish some, until the pond works out a system. So again check your local feed store.
And check with your local County Extension office. Some localities subsidize the cost of stocking waterfeatures, if they meet certain wildlife habitat criteria. I've heard some say that between tax credits, CRP, subsidies, etc. the various agencies may as well have built the pond for them. Do some homework, invest your time and save your money.