Mine would be how can you control colors of fish with food?
There are some color enhancing fish foods to buy that have the proper ratios of fat and carotene from what I've read. But also, be aware that they might not be as nutritious for your fish. You'll want to feed them other foods too.
Some fish do act silly. I think certain ones actually end up having their own personalities which have always fascinated me. I don't have a question right now but I will come back to this thread if I think of something!