Nice! I wish I had a 200g tank "laying around" hahaha...
I know about fish just by dorking out in the forums and researching online. Of course you can get fish shipped to you too if your LFS isn't great.
I love the butterflyfish - I have 3. They are unusual looking creatures. They do seem to enjoy each others company with a few quibbles once in a blue moom which just entails chasing. I'd definitely get a group as mentioned vs. one as they'll be more visible. They're not very active except at feeding time so if you just have one it might not be as noticeable in the tank. I started with one but when I got the other 2 they became more bold and seemed to help settle each other. I do have floating plants, which they like. For wild caught fish they eat literally anything I put in the tank at the top, from flake to floating cichlid pellets to bloodworms to thawed fish or krill. Love watching their huge frowny mouths open up to gobble up food. They'll even eat small pieces of frozen food from my fingers.
