Weird mounds on Nerite snails

I've noticed a lot of my nerite snails have these weird white mounds on their shells. The mounds are cone/pyramid shaped and if I look closely, appear to have kind of a feathery thing sticking out of the tip sometimes.

No clue what they are. Can't find one right now to take a picture unfortunately.

 

Sounds like a barnacle to me.

 

barnacles. i have em on my snails too, some of em. i got mine from reefcleaners. i kinda like em.

 

Just googled them, they don't seem to be those guys. The worms seem to have a more spiral shape.

The mounds don't have the same spiral shape. They have these vertical lines from the base to the tip. They kind of look like little volcanoes.

 

That's what they are and I received mine from RC as well. Thank you so much!

Are they harmless or should I be worried?

 

Harmless. I have a few that are a year old. Doesn't seem to bother the snail at all.

 

Its a plus for sure, they filter feed as your snail does its business. completely safe.