Here are the steps I take when shooting pictures of my saltwater fish tank.

I would try to not use the flash if possible, and if you can hold the lens right next to the glass straight on to keep things straight. Taking pictures of tanks is difficult if your tank doesnt have a lot of light (for my camera). Here are somethings I try to do when shooting:

• Turn the other lights in the room out
• If you have a lot of flow in your tank, turn your pumps off
• Use your lowest ISO you can as corals wont be moving
• Set the custom white balance of your camera (if you can)
• Turn on macro mode (if you can, usually a flower icon)
• Use the cameras “half-press” so the camera can focus and give you an aperature (brightness) value. You want this number to be about 0 a postive number means too much light and a negative number means not enough light
• adjust shutter speed and f-stop (if the speed is really slow) you may need a tripod (always helps) – then just hope something doesnt swim in the way
• Once I am done I usually open the pictures in Photoshop and adjust the color levels by using “Auto Levels” (Alt + Shift + L), this helps bring out the color a little better usually