Found it to be really tough. Need to try to match white balance. I also likely should have been using a macro lens, but it is what it is. Any good threads on Sony DSLR or overall DSLR settings?
Check the stickies at the top of the photography forum for ideas on settings and such. I use a custom white balance, then adjust in Camera Raw. I set my color temp all the way to 50000K, then adjust from there. I use a 200mm macro lens and my 28-70 f2.8 to shoot the tank. 28-70 is great for pics of the fish and scenes. Macro is fun, but I usually break out the tripod if I go macro.