What kind of camera is it and does it have a flash? I took my picks in a semi dark environment (only one or two bulbs on in the room) and the flash. Just had to take the pics on a bit of an angle so the flash would not bounce right back off the glass into the camera.
Quoted directly off the camera "Fujifilm E510 5.2 megapixels" I'm clueless about this sort of thing! It has a flash yes, will give the angled idea a go.
I don't use the flash on my camera when I take pics of my fish. I find that the tank lighting is usually more than sufficient and the colors come out much better. Also don't have to worry about flash glare !