I have been reading your posts so far and were very helpfull to me.
So i tried to take my first pictures of my also new tank.One of them came out pretty well.
I use the olympus c-750 and as for the settings i use the auto mode with some zoom on and let the camera decide just holding my breath when i take the pictures.
The lack of my experience as a photographer generaly is the reason that i failed using other settings so far but to tell you the truth the auto mode looks to cover me so far and i concetrate more to catch the 'right frame' in my picture
...Sorry for my bad english but it's being a long time since i used the language more frequently