Gweneth - that's a great shot of the tank (not to mention a really nice tank), how did you get such a clear shot of the fish and such good color? I feel like i'm the only one who can't capture my fish on camera clearly!
The biggest thing I did was put an 18w compact fluorescent over it. The actual light for that tank is a somewhat dim homemade LED fixture (it's a low tech tank). You really need lots of light for photos, though.
I think the camera settings were 1/100, f 5, ISO 400 and the white balance adjusted for fluorescent
Ah, you have a fancier camera than I do, I can not manually adjust setting, I believe that makes a large difference. But I never thought of trying to simply add more light to the tank, that's an excellent idea!
Here's my 34 litre (~9 gal.) Aqua One. It used to be a goldfish tank before I bought them a much larger one, but I've kept it running as a tropical tank for about a year now. This is before all the crypts melted and I had to start again.