I was seeing the hydroids every day for a while in my tank. When I looked them up everything I read said they were horrible, killed corals, and the only way to get rid of them was to manually remove them, and worse, that eventually you'd have to tear apart the whole tank because they'd take over. I spent every day manually removing the ones I saw, which was a huge pain; I removed a really nice piece of LR (that every dritter in teh tank seemed to enjoy by the way) because I thought they had come in on that; I removed my fuge and cheato from the back chamber (I have a biocube) because then I thought they were thriving back there and then getting into the tank ...
Fast forward 3 weeks -> They vanished, no corals were ever harmed, I call bs. lol