Keeping in mind that I live in a small city without a lot of selection, can you suggest a specimen fish that would do well in a 15 gallon fresh water tank ? I do not want an oscar. I've had those before. It would probably need a larger tank anyway. I'm open to any suggestions. ( a chiclid, a gold fish, whatever ) I'd like something colourful. It would be the sole occupant of the tank. Remember keep it simple. ( a more common fish ) Thanks.