Black sponge spreading

[BigShifter]

I got a bunch of corals from someone who was breaking down there tank. One of the rocks had some zoanthids and a black sponge mat. They said it had grown in their tank for a long time and didn't cause any issues. As you can see in the pictures, it is starting to grow around the zoas and it is even spreading to a another rock. Seems easy like I can take the rock and peal it off if I want to get rid of it or I can break the rock to separate the zoas and put the sponge somewhere else in the tank where it won't spread. Any thoughts on what sponge this is? It looks like black velvet maybe (https://www.aquaculturenurseryfarms.com/live-sponges/black-velvet/). Is this something I should try to completely remove from the tank? 

Thanks in advance. 

[Emerald525]

I had some of that in my tank. It didn’t grow that fast for me but I would definitely get it out if there if it is doing that already.

[goldenbasketreef]

Yes, you need to remove that from the tank of it will take over all your rocks.

If you remove the rock you can use razor blade to start peeling from base, it is thick like leather coral and has a mat skin that attached to rock.

[BigShifter]

Thanks for the advice! I will break that rock and then try pealing it away from the zoanthids. 

[Jack-the-reefer]

If it’s just zoas, you can soak the rock in 50% tank water, 50% hydrogen peroxide for 10 minutes. It won’t bother the zoas, but will probably kill the sponge.