IMHO don't bother with white balance in your what you shoot in a lighted tank, just let Photoshop fix it up with a couple of clicks. These three were adjusted in PS with three clicks each, Auto Contrast, Auto Tone and Auto Colour. Results would be better with originals

http://snaz.com/marine/PinkPanthersa.jpg

http://snaz.com/marine/Sexy1.jpg

http://snaz.com/marine/Zoas3a.jpg