What IS this thing?

[ophiura]

Looks like it will reach 3.5" to 7" or so. A bit large for a reef anyway, likely a bulldozer. I have not found a lot of info on them, but the family as a whole seems to be carnivores favoring snails and bivalves. Might be worth throwing a piece of squid or clam near it and see if it will go scavenging.
What sort of fish do you have in your FOWLR? Should be good for it unless you have wrasses, puffers, triggers, etc.

 

[phoenixrising]

In that tank (150 gal) as far as fish go there is a juv. Queen angel, a purple tang, a coral beauty, 3 golden butterfly's and on Monday am adding a goldflake angel. Also, there are probably 50 or 60 turbo snails and some scarlet reef hermits, and some bumblebee snails. I have been watching this fella trying to see what he is eating, but haven't seen him consume anything yet. No evidence of dead snails anywhere. Course, he's only been in the 150 for a few days when I chickened out and yanked him from the reef. Maybe he doesn't eat frequently enough for me to find anything dead yet. The reef is so packed that I may not have noticed the absence of a snail or two. I will try putting some choice morsels near him and see if he goes for it.
I believe he has already surpassed the 3 1/2" size and continues to grow. I think the bulldozing potential is large...another reason he was evicted from the reef, although he never knocked anything over in there.
Thanks again for all your help!