zoa/sponge

[debbie]

Hello all, I recently got a small frag on a plut of some really colorful beautiful zoas. Over the short time i have had them they are not opening much anymore and there seems to be a type of sponge now covering them. I just emailed the fellow whom I got them from and he said that the mother colony which is on a very large rock that he took from does indeed have a type of spong growing on it. He offered a new cutting to me but I might be in the same situation with it too.
I have removed it from the water several times to try and kill it but it does not seem to work I don't know how long i can leave it out of the water without killing the zoas??
I just moved it to a higher light, higher flow and took a toothbrush and some tweezers and removed a bunch of the sponge again.
Its now back in the tank, its not touching anything else as i have it placed on the sand bed for that reason.
Does anyone else have any ideas on how I can kill this sponge??

 

[speg]

Pictures always help people to better diagnose the problem.
Is the "sponge" like a white mass that's forming over them?

 

[debbie]

I cleaned it yesterday so there is nothing to take a pic of but I have found out that it is indeed "encrusting sponge" the guy whom i got it from sent a pic of the mother colony for id and that is what everyone told him it was.
So now how does one kill this stuff??