peppermint shrimp will control them. I had them pretty bad in my pipefish tank which gets multiple daily feedings of cyclopeeze and ova causing hyroid numbers to explode. I removed the 12 line wrasse from the tank and added a few pepps. The pepps went to town on the hydroids. They are still in the tank but the numbers are drastically diminished. Zoas are not irritated anymore.
These were mine--
