ID this encrusting growth please?

[JohnM99]

Lost most of my corals in a cooling failure a couple of years ago - didn't replace them and just enjoyed my anemones - I noticed that an encrusting growth slowly appeared over the back of the tank (acrylic overflow) - very slow but steady growth - looks like an SPS - quite hard, but surface is soft and smooth - with some long thing tendrils growing out several inches, maybe 1/4 to 3/8" thick. It has also grown over some live rock. Color is described as ugly brown by my wife, dark green-brown by my son, and since I am partly color blind, I just agree.

Now I am revitalizing my tank and going back to corals -

Wondering
1- what is it?
and
2 - I am upgrading my lights to an ATI T5 6x54 W setup - I have been running a Sunlight T5 hood with only 2 of the lights working. I also put in a Phosban chamber - my phosphates have been kind of high. Nitrates were 5-20 - now well under 5. pH ~8.2. - do you think I might be able to knock off the brown zooxanthellae and induce some nicer color by changing the lights and cutting phosphates?

I would hate to scrape it off if it could change color.
Photos in my gallery - will try to attach but not quite sure how.

[JohnM99]

Here are a couple of photos (I hope)
http://reefcentral.com/gallery/showphoto.php?photo=276693&papass=&sort=1&thecat=500
http://reefcentral.com/gallery/showphoto.php?photo=276694&papass=&sort=1&thecat=500

[woodiecrafts]

Judging by the pictures to me it looks like a montipora of some type. My Monti caps have the same texture to them. The color really throws it off though, but under the type of lighting you have now, a purple monti cap will look very much like a dull brown.

You new choice of lighting will definetly help everything out and in time, if it is a monti, the coloring should come back. Others that chime in may have a different idea on it.

[noahm]

Scrape a bit off the wall and see if it actually has a calcium skeleton. I do not see any polyps, but do see some pores that lead me to believe it may be an encrusting sponge of some sort. I have a yellowish green type that looks almost identical growing on the face of one of my rocks. If it is SPS, it should have actual polyps extending at times.

[JohnM99]

Yes it does seem to have polyps - I do not think it is a sponge. The polyps are very tiny, white and thread like.
I did have a hydnophora at one time - and also a small Montipora cap fragment - could have come from those.
That is encouraging - fixing up my lights and water may make it more attractive.
She Who Must Be Obeyed will be pleased.

[rendogg]

Definitely an encrusting sponge.

[briangg57]

My monti cap. has areas where it encrusts the rock and it looks EXACTLY like that.

[rendogg]

The first photo and the "soft and smooth" description points to sponge, not montipora or any other hard coral. I have seen this sponge before but can't ID it. It may become a problem as a lot of encrusting sponges will compete and war for territory.

[JohnM99]

It has a rather hard and firm structure - the twig like extensions that have grown out are flexible - although break off easily - so it does seem more like a calcareous sponge in that way. They do not snap like say a birdsnest coral branch would.
It does have very thin white wavy tendrils that stick out - about the size of a small sewing thread - do calcareous sponges have these?
If it is a sponge, is there a chance it will change color with changed environment?

[noahm]

If it was a monti, or any sps, the polyps would be quite uniform in the form of a ring of stubby fingerlets, even if they are quite small, and would retract as you run your finger across them. The thin wavy tendrils could be another life form living on/in the sponge. The sponge I have is quite firm, though very slippery smooth to the touch, and has that very same kind of surface that looks like someone stretched a plastic tarp over some rocks and pine needles. My yellow encrusting sponge changes from dark mustard to more of a greeninsh/grey yellow in different areas on the same colony.

No saying it is a sponge for sure, but that is my vote from the pics.

[luther1200]

I have something similar to that. I have no idea what it is.

[JohnM99]

So, it is probably a calcareous sponge. What do you think about the chances of it changing color with a major change in lighting? I see Noahm has one that is differently colored in different places - mine is pretty uniform.
Would you keep it? Or scrape it off?

[noahm]

I doubt it would 'change' color, so much as new growth may be slightly different depending on tank params and nutrients at the time of growth. It it non-photosynthetic, so light shouldn't affect it... mine is relatively uniform, just ranges slightly from more yellow to more green.

It seems that some people have had them spread around, but mine usually covers the side of one large rock and then it will inexplicably recede for a while, then grow back some. I just leave it alone. It looks pretty happy, so you may want to keep yours in check a bit if it starts to get too happy. Other than that, if it was an encrusting monti on the back wall, would you have kept it? If it looks the same, why not keep it?

[username in use]

If it is a sponge and you uprgrade your lighting, it may become overgrown with algae. The low light could be whats keeping it happy, as they tend to pick out the shadier spots.