Larry, I have absolutely no knowledge of cameras! I just set it to automatic and let the camera choose the settings.
For my tank shots, I turn off the flash and try to hold the camera still. (Don't have a tripod.) I also try not to have lights from the room reflecting on the tank glass. Turn off the lights or cover windows during daylight.
The fish won't be in focus, but without the camera flash, you won't have that terrible reflection that washes everything out. And like Anthraxx said, if you want to use the flash, try it at an angle.
I just reread your post, Larry and see that you tried it with no flash. I'll look at the info on my pictures and see what the settings were and let you know. . .
Exposure Time: 0.167 s (1/6)
Aperture: f/3.8
ISO Equiv.: 800