Thanks for your kind words everyone. I appreciate them.
James, I do have a shot of the informis but it's a boring photograph. While it's a beautiful, unusual color, in the pic it looks mostly like some brightly colored vinyl or plastic with very little contrast or visually interesting things going on because the base and the polyps are the same color.
Louis and o.c.d., in general I'm shooting these in RAW with just the tank lights (2 400w 20,000K MH Radiums and 2 T5 Giesseman Actinic plus), in a medium high fstop (11-14) and too slow to hand hold but not that long shutterspeeds, say 1/2-1/4 second. Of course I'm using a tripod, pumps off and shooting straight through the glass. I also shoot remotely with my laptop, so I'm looking at Live View on my laptop display, which (being 15" v. 3") helps me to focus and to compose. I can't recommend an exact exposure as for me it varies depending on how high or low in the tank the subject is.
Jake I am not focus stacking any of these and I would like to. Grant got me thinking about a plywood "stage" on which I could place my tripod (gaining stability) and then just slide the whole piece of plywood a tiny amount with each frame exposure. One day I will do that...
I am fortunate that with my lighting if there is nothing immediately behind the subject, the background tends to fade to black or at least be beautifully diffuse.
I am shooting entirely in manual these days which I am enjoying. It forces me to think harder about each exposure and I'm doing a lot of bracketing of exposures so I end up with something usable. When I'm done shooting I can pick the image which is plenty bright but not overexposed. With corals tending to have super bright, easily overexposed tips and darker, shaded bodies with interesting textures and markings, using judgement about when some slight overexposure is ok is necessary.