[Member No. 1]

You should pose this question in the Photography forum. There is a lot of good info there.

Cameras have a hard time with the blue light people tend to flood their tank with. You can add a yellow filter to the camera to help correct some of this, but it still won't give you the results you are looking for.
The really great shots you see are more than likely shot in RAW format and then is post processed in Photoshop for color correction.
It's really easy to do. Another trick people use is to focus stack. Basically this taking a series of shots by moving the camera toward the subject on a focus rail but without refocusing, then having Photoshop merge the shots together.
There are some great videos on Youtube about taking reef tank pictures, how to shoot in RAW then color correct, and how to focus stack.

A good macro lens is also key to great pics.

Go check out the Photography Forum.