Oh, believe me, I know about the cost of developing fish shots. When I first started, I would get flash-in-the-glass and have to toss endless slides unless the flash could be cropped out. Then I'd get perfectly focussed photos of air bubbles, the filter, the algae, or the gravel with the fish waving "sayonara" with its tail.
I love digital cameras, and when I clean the glass and do my next maintenance, I'm going to set up some shots. I don't have photos of the fishes I have now, and it should be fun with the digital camera. (Now that I know your trick.<G>)