I think it depends on how blue your lights are and how far your camera's white balance will go. After you take a picture, your camera tries to guess the color of the lighting and remove that color cast. Incandescent are yellow. Flouresent lights are green. With really blue tank lighting the camera just wasn't designed to consider a light source that blue. As a result it only takes out some of the blue cast. I've found that Lightroom (a photo editing program) can't fully color correct a photo taken under just blue actinics. While it can do better than the camera, it is still limited.
Some ideas to experiment with if you can:
- try using whiter lighting over your tank (turn off actinics)
- try just a few photos in RAW and correcting white balance in a software program, if it helps then you've narrowed down the problem and maybe we can help further
- try manually setting the white balance on your camera (if available). The camera will ask you to take a picture of something white, like a blank sheet of paper, under the target lighting.
- try shooting in JPEG with a "vivid" color setting to help boost color saturation and contrast