Are these colonial hydroids?

[bossjx]

These things have been here for over 2years now when i first bought the tank. Havent seen them anywhere else in the tank.The green circle gets much brighter when lights are on.

 

[Crabs McJones]

Looks like it to me

 

[bossjx]

Looks like it to me

should i try smothering the whole rock with putty, will be hard to remove that rock and put the scape the same as it supports like 30 lbs of rock.