Clean the insides of your tank glass and outside as well. Do this in advance of taking any photos so the water is clear. I am preusming it is a digital camera. If you have a tripod (or use a stool or a bench) being careful that your camera is secure. You can use a smaller tripod on a table to bring it up to the height of the tank.
You could try setting your timer control on the camera and then taking a full tank shot of your tank. Once you have this photo you could crop it in a photo editing software on your pc.
If you take it with the tank lights on and all the room lights out and turn the flash off on your camera you might get quite a nice shot because this reduces reflections. If your camera has a macro function or closeup function you could try moving it closer. Try to take photos of stationary or still things first in the tank as these will not blur as much because they are not moving. you can place a bit of card on the side your camera lens to reduce reflections on the glass.
1. Clean your glass
2. Steady your camera
3. watch for reflections and remove them. either turn the source of the lights or block the reflections
4. maybe turn the pumps down low for a minute. This will settle things down if they are still blurry.
5. Shoot at right angles to the front glass to avoid aberations
6. Turning off the flash can reduce glare.
7. If you can't turn of the flash shoot at 30 degrees to 45 degrees angle to the glass to reduce reflection.
8. make sure you have all the tank lights on.
For point and shoots experiment with any night settings etc.
These tips might help.
