On camera I mostly use Auto WB for most situations.
For fish/reef tanks I use "Preset WB" or "Cloudy -3".

I shoot RAW most of the time now. And that does make it easier IMO to change WB in post processing as well as other settings especially when using Nikon Capture or Photoshop.

For programs I use : Nikon Capture, Raw Shooter Essentials, PSP-X and Neat Image. Someday I will get Photoshop. For most things though what I have works for me for now.