The best thing to have is a canon 550 D or 600 D with a macro lense for the finer details. Alone though, either of these cameras will cost you $1500 and the lense around $800, so they are pretty pricey. Also I'm not to sure, you may want to get a tripod as well, espically if your tank is tall. Tripods are worth having anyway. You can get a tripod anywhere between $30 to $700 dollars, but it all depends on how much your cameras going to weigh, but buying a more expensive tripod will definitly benefit your images in the long run.