A forest of hydroids

[sharuq1]

You could try putting kalk or joe's juice all over them. I had this problem really bad on one of my rocks once and had no kalk/juice to take care of it, sadly I had to torch the rock with a blow torch to kill them (also had to torch some bad algae I couldn't get rid of but that is another tale), and you know what? frickin buggers...some still lived, lol!

If you want to go double on their hydroid butts juice/kalk them and then cover them with putty or something. I don't think much could survive that...I would hope...