Tips for in tank shots of corals:
1) Turn off your pumps.
2) Get a tripod, even a Walmart cheapy.
3) Shoot straight through the glass. Any angle will cause diffraction.
4) Set your white balance. I used a Styrofoam plate. Check the manual on how do do it exactly.
5) Put it in manual. Set it to manual focus. Set your aperture to the low #(your depth of field will be shallow though), shutter speed low(corals don't move with the pumps off), ISO around 400-800, fire away. Use your self timer(unless you have the remote shutter release) to reduce vibration. Look at the histogram on the camera for exposure guidance.
You could also try putting it in macro mode as a start.
Any auto mode on the camera will be less than ideal.
Edit:
Looks like Dave beat me to it!
Speaking of Dave: perhaps having Jennifer(princer7) give a photo how to at one of the sponsor's, or member's house, would be a great meeting. She helped me immensely!