I agree with Rick James, it does look like a Hydnophora to me as well.

I have some of this stuff and I am pretty sure its hydnophora.

I got this piece from The Coral Hunter. He Had a specific name for it that I had never heard of before. It wasn't Hydnophora though. He said it was a rare coral that came on one of his shipments. Guess I will never know :sad:

Harvey,
I have a piece just like that in my tank and I never knew what it was either. What would the rest of the name be? Pavona what?

Don't trust the name they call it at the store, they are often not even right on their order sheet. The polyps on that piece look hydno-ish to me. Maybe this one since it looks like an encrusting growth form?

http://whelk.aims.gov.au/coralsearch...0pages/215.htm

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What kind of lighting do Cactus corals prefer. My frag bleached a bit after my light upgrade and hasn't recovered yet. I have kept it up high under 400 watt MH, too much?

I think you are right, I found the recipt for the coral and it is listed as a Pectinia Coral. Did some searhing and found nothing like it so Hydnophora it is :mrgreen:

Mine is under 400W about a foot below the surface, hasn't bleached but also hasn't grown much in the 4 months i've had it.

I would guess Psammocora contigua (not Pavona sp. anymore).

The First item is Psammocora contigua This coral is often overlooked by hobbyists as it often arrives brown. I've had many of these turn emerald green or brick red after settling into the reef. Cat's paw refers to numerous species.

As to the second one I'd say maybe Hydnophora exesa

but more likely: Pavona explanulata
Can you get a closer picture of the polyp structure?