Best Pictures with what device ????

[Scythanith]

Some quick tips:

Always shoot straight through the glass, NO ANGLES!
Turn the pumps off when you shoot to limit polyp motion.
Shut lights off outside of the tank and wear a dark shirt.
Use a tripod.
Play with aperture to get what you want in focus, up the ISO if need be to get a fast shutter speed and less motion blur.
Try and set a custom white balance if your camera allows it, if not, shoot in cloud mode or 10000K.

Top down is the best way to shoot. Get a top down camera box.

Have fun!