I have read that the only way to get rid of hydroids is to use a tweezer and pluck them out. If a rock is badly covered in them and is probably impossible to clean off with a tweezer am I best just to get rid of the rock? I've tried to remove as many as I could but there is just to many and some are in crevices that can't even be reached. Will they die if I leave the rock out of water for a while?
I had them in a tank years ago, but i think i was calling them something else.
From what i remember they were just on the glass and were not causing any problems. But there were literally hundreds on the glass and at times it was kinda unsightly. Dont recall if i did anything to rid them but eventually they subsided.
I would monitor the tank and if nothing seems distressed then i wouldnt worry about it. If there on the glass guess you could use a net to scrape them off....wont rid the problem entirely but may reduce the population slightly.