Kellehar, What camera are you shooting with?
Most cameras have a "P" program mode
"A" aperture priority
"S" Shutter priority
"AUTO" mode
and a bunch of preset funky modes
I would suggest you use "P" to start This will automatically set exposure for you. Turn the flash off. I will put my lens directly against the glass. This will eliminate any reflection
Many cameras will have metering modes. These will help a lot for ensuring correct exposure of you subject. Spot metering is good when shooting something that is lit and the back ground is very different. Like a fish on white sand. Average metering would be good for full tank shots.
There is also usually some "MACRO" Modes this will allow you to get subjects that are too close for the camera to focus on in regular mode.
It is very difficult to hand hold a camera if the shutter speed is greater than 1/16 and for me I can't hand hold anything slower than 1/125. so a tripod is a very good idea.
I hope I haven't rambled on about things you already know if so sorry.
Any ? let me know
BTW IslandReefers right "take lots of pics and delete the bad one
