You will find this out sooner or later. The bigger the tank, the more stable, and easier to take care of. I can't tell you how many fish I lost early on when I had a 10 gallon tank. Them I moved up to a 30 and it was much more stable and forgiving. Not that a 10 gallon can't be done, but it can be tough when starting out. Be ready to do some water changes when you start to have ammonia start to show up. Or you might want to start changing a couple gallons a day to keep ahead of the game since you have a live fish in there.