What type of hydroids are these? and are they bad.... I've scrubbed the shell since this pic but I'm curious what they are. The snail came from the LFS like that and I do know there's others in the tank. There's more in the tank came from a frag plug and look similar but I'd say there are little orbs at the end of tentacles instead of bushy like those ones. Also are they safe to toothbrush off rocks as I see them or will that make them spread more? Thanks!