What is this black stuff spreadin on my rocks?

[Seansea]

It's growing out from back of this rock onto my zoas. It's not algae nor cyano. It's literally growing out from total darkness. It's growing onto my zoas. I was thinking maybe a type of sponge but I'd it was sponge my dwarf angel would be having at it. Zoas don't seem to be happy about it. Anybody have this and come up with way to stop it?

 

[ISpeakForTheSeas]

It's growing out from back of this rock onto my zoas. It's not algae nor cyano. It's literally growing out from total darkness. It's growing onto my zoas. I was thinking maybe a type of sponge but I'd it was sponge my dwarf angel would be having at it. Zoas don't seem to be happy about it. Anybody have this and come up with way to stop it?

Colonial tunicates - looks like an invasive variety (theoretically fine on an isolated rock by themselves, definitely not fine with access to the rest of the tank); these shouldn't be chemically harmful, but they can be invasive to the point of growing over healthy corals and smothering them.

I'm not sure of the best way to remove them without harming/irritating the zoas. I know these can be killed by drying out or soaking in freshwater, but I doubt the zoas would appreciate those methods. You could try manual removal or common sponge removal methods like injection with boiling water or something, but that seems risky with the zoas.

Honestly, I don't know if it would work, but I'd personally probably try "feeding" it DIY Coral Snow (basically powdered chalk) and seeing how it reacts - if the little holes close up, then you might be able to just dose enough to keep them shut until they starve out, but definitely no guarantees there.

 

[Seansea]

Oh jeez. That sounds bad. Ya them being on my zoas isn't good. But don't want it spreading anymore either. This sounds bad

 

[TokenReefer]

What is the orange coral in the center?

 

[ISpeakForTheSeas]

Oh jeez. That sounds bad. Ya them being on my zoas isn't good. But don't want it spreading anymore either. This sounds bad

Yeah, I'd try the coral snow, and if that doesn't work then you may be able to try a few different experimental removal methods like attempting to dehydrate them from the inside out or something similar.

The colonies are a bunch of little critters that are basically just mouths called zooids; they basically share a skin and a centralized out-current siphon; so theoretically you could target just them and kill them from the inside, using their shared skin to try and shield the zoas from the worst of the effects.

 

[Seansea]

What is the orange coral in the center?

Blato merletti. I forget the name of them. This photo takin in sunlight thru windows. They pink outside with purple center. Cool lookin

Yeah, I'd try the coral snow, and if that doesn't work then you may be able to try a few different experimental removal methods like attempting to dehydrate them from the inside out or something similar.

The colonies are a bunch of little critters that are basically just mouths called zooids; they basically share a skin and a centralized out-current siphon; so theoretically you could target just them and kill them from the inside, using their shared skin to try and shield the zoas from the worst of the effects.

This seems like will be extreme challenge without effecting zoas but they not doing great anyhow with these guys growing up on them. Seem to be spreading fast