How to take fantastic pictures of fish:
1. If you don't have a good camera, rent or borrow one (alternatively buy a model or two older and buy used from a good source)
2. Find someone with a macro lens that will let borrow it. (Alternatively, borrow them)
3. Take an obscene number of pictures
4. Find someone with a photo editor to fix up your deficiencies (color, framing)
There have been winners of the photo contest who won with an iPhone shot. The key is to find something about your subject that you find interesting and try to get a picture of that.