Nuke rock

I have been told you can cover them with Kalk paste and that will kill them. I would imagine a week or two in the sun would do it too. I would not bet on the freshwater bath, however.

I recently had a bad outbreak in my 30 gallon tank that killed off a nice rock covered with zoas. I ended up actually taking the tank down, (I also had an aptasia problem going) and re-cycling the tank with all new live rock.

That worked, too. I simply vinegared out the tank and started over.
 
A week or two? Heck, I have had liverock out in the AZ sun for two days and everything died. Wash it off it RO water and you're ready to go.

I bet a few hours out in the afternoon sun would probably do but a few days to be sure.
 
Have you tried to laser them? I have also heard of people taking the rock out of the tank and blasting just the hydroids with boiling water from a syringe. do not let them attack that anemone!
 
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