I use a tripod for some of the pictures. Most of those pics were taken with a tripod, except for the over head shots and the clown fish/anemone shot.
I use the timer to take the shot unless trying to shoot a fish. It's a poor man's remote shutter switch, I hit the button, wait 10 seconds, and an absolutely still camera takes the shot.
I adjusted the white balance against the sand bed, which removes alot of the blue from the tank's color that isn't seen by the eye, but picked up by the camera. The picture of the hermit crab is the only one taken on automatic mode and you can see how blue the sand is. I just kept finding a good white spot until the colors came out true, it was a PITA and took me several hours. I think a combonation of sand bed samples and white paper against the tank glass were used to get the right white balance setting..but it's been awhile since I did it.
Most of the pics are taken with the exposure at -0.7 or -1.0. All of these pics are at -0.7, but the one of the small toadstool is -1.0, which is why it's so dark. -1.0 takes the sharpest pix, but they come out over shadowed.
A tripod really helps alot. You loose the ability to shoot at any angle, but your pictures come out clearer. So full tank shots, etc, all come out much nicer. I think I've almost milked this camera for all it's worth though, and I cannot get very good macro shots...but otherwise it's okay.