What is on my snail?

[RDReefNYC]

Any idea what is growing on this snail?
Have had the snail for about a month and this just showed up suddenly.

 

[Reefkeepers Archive]

Hydroids, are said to sometimes irritate corals but I have them all over my tank and they aren't causing problems, though you could take the snail out and scrub its shell, with exactly what I can't remember.