ReeferMac has the G4, but I think technique is similar for my Canon A70. I set resolution to maximum size for a big pic. I usually choose Macro mode with auto exposure- flash off. Keep lens pressed against aquarium, or at an angle if using flash. You'll still need to edit your pics- not every picture is as clear as you thought it might be. Sometimes taking a picture at a distance {4ft. or so} from the tank on max resolution will capture something unplanned- like a fish diving into the sandbed. You'll have a big pic to play with {crop}. You have to play with your camera! Can't wait to see those frags.