ID hitch hiker worms ?

[Lex_510]

I have tons of these all over rock and want to know if their a pest, bad, or hurt anything? And if there’s any crab or fish to get rid of them. Setting up a bigger tank and I wanted to know if I should bleach the rock to get rid of them and start over

 

[RedFrog211]

Digitate hydroids

 

[Mikedawg]

They seem to come and go for many reefers; I wouldn't worry about them - you could brush off with a toothbrush, but they are part of the diversity of a healthy tank, imo.