Thanks everyone.
millym,
I've been into photography for 16 years, mainly macro nature shots, so I've learned alot of things over the years. When I first started macro shots I might have ended up with 4 good shots on a 24 roll of film. Then all of the sudden one day, might have been close to a year, I would get 20 good shots on a 24 roll of film.
For fish pictures I use the flash on the camera and take the picture on a slight angle so I do not get any glare from the flash. I also took these pictures in manual focus mode. Using the auto focus did not focus were I wanted it to.
When shooting, the larger the F - stop the more depth of field you will get. This results in a larger area that will be in focus but will also cause your exposure time to take longer. Which can have you shake the camera or fish move and cause a blurred image. Because there is usually not much light in the tank, if auto mode on the camera, it will pick a smaller f - stop to gather more light and shorter exposure time. Which results in less depth of field and less chance of camera shake or fish movement. It's a balancing act alot of times.
If shooting digital just keep shooting, trying different setting and seeing what changes happen.
bittersweet,
I use a Sony 707 5 MP camera.