I'm a sports photographer by trade and taking photos of fish/aquariums is very much like taking action sports shots....for every 25 to 35 frames spent you'll get 1 "sellable" photo! Pros suffer from the same problems your having. I use a Nikon D5000 digital SLR camera...use to be the most expensive digital camera on the market...still use the "garbage can" button more than any other on the camera!!!!! Now, I can set exposures and appatures fairly well, due to nothing but experience, but as far as "capturing" the great shots....get lucky, baby!!!