Sam,
You should try playing with your white balance settting, you can get some really good results sometimes. By no means am I telling you how to take pics Sam
, as you are aware that I think you take some of the best images on the board, this is just a suggestion to try another feature that digital camera's offer.
I use my setting quite a bit when I want to get good coloration without having to take long exposures. I simply take a WB reading of the front of the tank by taking a shot pointed at the tank while my manual WBS is on, and then I just start shooting from there.
If you don't like the results your getting, just take a picture of a white wall or white board or dial your setting back to auto WB. Like I said above, to capture true color from some of the corals and fish in our tanks we need to take long exposures, but if the subject is moving then we can't, so the WBS allows us to do this by adjusting to the colors that are found only in the tank.
Here is a recent image of my brain using the WBS, if I did not use this setting I would have had to take a much longer exposure with a smaller aperature setting otherwise the brain would be overexposed and look fuzzy or tend to glow or glare a little, and with a longer exposure the clown would have also been blurred or out of focus. You can also see how the WBS that I took of the tank didn't effect the white stripes of the clownfish, they still turned out a nice white.
