What are these

[Hethari]

On a small rock I found multiple feather duster like with a firm stalk only tentacles retracted opinion please I'm afraid they are aiptasia

 

[Pete polyp]

Hydroids

 

[ScottMyers123]

+1 on the Hydriods

 

[DED65]

The Aiptasia that I have will retreat completely into the rock, no firm stalks.

 

[Hethari]

Harmful or what

 

[Tahoe61]

Hydroids can become invasive. Some report that the pest stings corals other report that their corals were not bothered by them. Hydroids can become unsightly if they do become invasive. Do not over feeding the tank as this will lead to an increase in population. You can pull them off with tweezers or place a piece of underwater epoxy on them.

 

[Hethari]

Thanks guys

 

[Hethari]

It's a small rock took the Zoa off and removed the rock

 

[ScottMyers123]

You could do a bleach bath and then soak in R/O water then return the rock if you want to use it.