When I first bought my snails there were white bumps that had holes growing on it's shell. I thought it was sort of bad. Well, today after 2 weeks of having the snail, I found out that they were BARNACLES. I was so amaze. First i thought they were feather duster, but they didnt have tubes and they were in a color of bumps with holes. Are these bad or good? How long would it take for them to spread?

barnacles are not bad, they are filter feeders. If your tank
is fairly new they won't spread, not enough food.

Thanks Eznet2u. I was born so I tooked a video. It also have the snail with the barnacles in it, but you will just see the whiute bumps not they barnacles itself. Here it is. :D My first time so enjoy it.
Video