Whats the brown stuff growing on this zoo rock?

[SuperLes1]

Something brown is spreading on this rock and I don't know what it is?
I put this Zoo rock up next to my tank wall and the brown stuff started to spread onto the tank. Is it part of these orange and brown zoos or is it trying to take over? What is the brown stuff? Good or bad?

 

[impur]

Looks like some sort of encrusting algae. I would get it out of there, try to frag the zoas away from it and toss the rock it came in on.

 

[A. Grandis]

That's a type of algae.
Is it hard or soft?
Looks like brown calcareous algae on the glass and on the polyps.
It looks like that it's kinda suffocating the zoas...
Try to remove the colony out of the tank and scrape really carefully the algae, cracking it and removing it's fragments from the zoa colony.
Rinse lightly with salt water in a bucket and put the zoa colony back in the system.
If that is what I've sad, probably means that your Ca and Alk are in good balance!!
You have left it growing for a while!
Good luck!
Grandis.

 

[kershak]

i think its a sponge some zoas have incrust in tha stone remove fast because that thing stress the zoas and kill them

 

[mallorieGgator]

I think it's a sponge and it needs to be removed carefully from your zoas and from you tank.

 

[A. Grandis]

If that's sponge, maybe Hydrogen peroxide would work. Remove the rock out of the tank, apply HP on the base of the polyps avoiding the mouths, and try to remove all the dead stuff away from the colony. Rinse with saltwater from the tank and return to the system.

Try first to remove like I posted before. You can use a soft tooth brush or Qtips if it's sponge.

Unless anybody else knows better treatment...

Grandis.

 

[jascymcl]

If it is sponge manually remove it , it usally just pops of with your hand.If any thing is left just at a toothbrush to it. Will come right of the rock.No that type of sponge does not kill zoas , but it does not look esteticly pleasing.