I think something to remember is that, to get one GREAT photo, you need to take LOTS and LOTS! As well, taking photos of fast moving fish is likely to make you frustrated when you're first starting to learn. This is a very challenging task! Try instead to take photos of more stationary items in your tank (corals, inverts, etc.), fiddling with depth of field, shutter speeds, etc., and then when you're more confident in what you're doing, move toward fish pics. For what it's worth, I really don't try to take pics of my fish. Too frustrating
Do you have a tripod? This can also help with achieving a crisp, un-blurred photo.