Glue over hydroids

[SamMule]

Found a small colony of what looks to be hydroids on one of my rocks this morning. I know... The pic sucks). Covered that area of the rock with BRS glue to smother them.
How long until they starve out and I can remove the glob?

 

[myinvalidname]

No need to remove it. It will disappear under some coralline algae or bio film fast enough.