Did this Yuma build a "house"??

[dixiedog]

I posted this first in the Reef Discussion forum, but got no responses and I'm really curious. Maybe some experts hang out here.

Okay, so I put this Yuma in a spot with higher flow than he liked I'm sure, and maybe more light than he liked as well, what can I say, it's an SPS tank. But check out these photos. It's like he built a little shelter (it's rock hard) that he retreats under from time to time, almost completely hidden. Pops right back out when he wants to.

Is this something common and I just never heard of it, or is my Yuma a freak of nature? Sorry for the bad pics, but you can see what's going on. Here he is in his purple "house" or whatever ...

And here he is out on his porch:

.

 

[scuba guy ron]

looks to possibly be covered in cyanobacteria.

 

[dixiedog]

No, not cyano, it's like a lean-to roof, and hard as a rock. If the Yuma died the little roof would remain forever.

 

[scuba guy ron]

they are a low light coral. if it is moving to a shaded area (which they will do from time to time) then chances are it is getting too much light or flow.

 

[dixiedog]

It didn't move. The structure just came into being somehow.

Either the Yuma built it or something else did; I'm trying to figure out which.

 

[gh0st]

It appears to be a little shelf of plating coraline algea, which just happened to grow near the mushroom, or which the mushroom crawled under.

 

[Scott-CapeCoral]

I agree with plating coraline. I have some that is, thankfully, growing over some blue cloves.

 

[dixiedog]

Plating coraline! I had not seen or heard of that before. That is DEFINITELY what it always looked like, coraline, but I didn't know coraline "plated" like that.

What a coincidence, that it should first occur in such a place, and that the Yuma appears to benefit from it.