Thanks for the comments.
Nikon D100, Nikkor 105mm f2.8 micro, 200 iso, 1/80s, f3.2 (I never record the exposure but the camera does)
The fish was just sitting at the front of the glass. I used the natural aquarium lights—vho sun and actinic. The camera was handheld on autofocus and I just shot away. I have 6 almost identical shots.
Post processing—crop unwanted snail on the glass, my aquarium glass is scratched so I removed a large scratch with the PS noise and scratch filter (since the background was already out of focus from the large aperture this was easy), adjust levels, downsize to 640, unsharp filter
The background is a large brain coral. I didn’t adjust the color. The D100 camera gives a reddish orange tinge to browns under actinic lights. It looks OK to me, but from your reaction maybe I should adjust the color.