Old thread, new info. Powerwashing the rock they're on seems to work very well
I just went ape on the rock in my nano that was
infested with them, I thought I had them localized to one rock but upon further inspection they were rampant everywhere. Since the nano got nuked I thought it time to rid the tank of its excess of grape caulerpa and hydroids. I'm happy to report that they are no match for the mighty power of high pressure water
