With power comes complexity. What camera do you have? Another club member might have the same/similar one and be able to help/translate.
Some tips...
Have camera parallel to the tank. Shooting at an angle will cause distortion.
Always use tripod.
Use cable release, remote control or self-timer.
Room should be dark.
File format should be RAW. Gives you the best chance for color correction.
Many medium-high end cameras can do custom white balance. If you can't figure that out, put some white object in tank for a test shot. That can be used for color correction after the shot.
Use Manual focus.
Take lots of shots. Electrons are cheap!
Practice lots.