Here is some of the hardware I use to capture aquatic photographs.
The Nikon D70 and the Nikon 50mm 1.8d lens with the SB800 Speedlight were used for most of the images on this gallery site.  I have recently added the Nikkor 60mm f/2.8D AF Micro lens to my bag.  Many of the more recent photos were captured with this lens.  The custom mirror bar was created to work around walls.

Bouncing the flash off of high gloss photo paper creates a more even and farther dispersed flash.  The larger the "bounce box" the more light reflected back into the tank.

         Above setup is over the "built-in-the-wall tank".                                 This setup can be used on any tank. Very portable.