+1 on the used d40 idea. When you get a macro lens for it I would recomend getting something at least 80mm. Otherwise the working distance (closest distance focusing is possible) will be too short to utilize the maximum reproduction ratio (you would have to get into the tank to get the full 1:1 ration) You should be able to get a used sigma or tamron for cheep enough to fit your budget. you will also need a tripod. A slave flash might also be nice. you can get something like a vivitar used for very cheep.