A single strobe can create a very harsh black shadow on the opposing side, the effect can be pleasing- but it will definitely be pronounced. Most photographers I know are always shooting with two strobes.. you can always point one away and just use one of them.
The cool thing about fish that live in holes is you just have to be patient.. they will come back out. You can see the circular flashcube of the Ikelite strobe as a catchlight in his eye. I knew that the dark color of this Blenny would be a problem against the white coral so I let the coral over expose, and made sure the Blenny was bright. This shot is nice but I have a former student named Iyad Suleyman who has truly made an art out of shooting Blenny Portraits. His work is worth looking up- especially if you like Blennys and also Super Macro.
Shooting free swimming fish like these is a commitment. They do not hold still, so if you decide to try, plan on spending a few minutes and coming up with a lot of tail shots. Shutter lag on a camera is almost prohibitive for these types of images- but you can always get lucky.
