Is this black normal

I noticed this black by on my zoa rock and is now starting to form on the main rock, is this where new zoas are going to grow?

 

No they form by matting. It looks like a type of sponge maybe, hard to tell form the pic.

 

ok, i think its fairly new i dont recognize it, ill see if my phone can take a better pic

 

I have found them from time to time. they are normal although I have heard sometimes they can grow over corals and smother them.

 

so just a sponge, i wont worry then, just hope it smother the zoas, alhtough they are growing like crazy so wont really hurt them, just dont want it taking over

 

it seems like something that would be pretty difficult to get under control if it becomes a nuisance dont you think?

 

+1 Black Sponges can be incredibly invasive given the conditions are right for them to grow.

 

any idea how to remove, its starting to spread to the main rock

also, are they just able to pop up out of no where because i think this is a fairly new sponge

 

Ehh, sometimes it just happens. Sometimes, it's aliens.

 

IME they aren't nearly as bad as apatasia or majanos but you do have to scrape them off of rocks to remove them.

they seem to like specific spots and stick to them.