Need assistance with strange polyps taking over tank

[joe2]

I'm not sure if these polyps are attacking my corals or not but the ones growing close to them seem to be receding slightly and I'm concerned as these polyps are multiplying fast. the strange thing is, i'v not added anything new to this tank in forever and these popped up out of nowhere and are spreading rapidly. They look like the common yellow polyps but are only 10% the size of those and unlike the common yellow polyps, these polyps retract into tubes like feather duster worms. Any ideas?

 

[smartwater101]

Do you have any pictures with daylight instead of blue? First thought was Aptasia but I can't tell. Although I am on mobile at the moment lol

 

[Neo Jeo]

Looks like Hydros

 

[smartwater101]

Maybe Parazoanthus gracilis? Do the look like these in white light?

https://reefbuilders.com/2015/08/18/5-invasive-corals-that-border-on-being-aquarium-pests/

 

[joe2]

No, as stated, they definitely aren't the common yellow polyps which would be Parazoanthus gracilis....they have tubes they retract into (which also eliminates aiptasia.). These aren't a common pest as Im familiar with the usual suspects..this is something a bit more rare.

 

[WV Reefer]

Looks like colonial hydroids to me.

 

[joe2]

Yes...I googled them, and that is definitely what I have. I'm reading that some people say they didn't harm their corals and others are saying they did....I wonder why so much variance in the problems they cause...maybe there are multiple species that look like these with some being harmful and some innocuous?

 

[ReeferReefer]

I second Hydroids.

Not sure on the variations.