That was my first guess also VictorFancy slugs with hairdos are nudibranches.
from what i can see from the pic the one on the tank glass i would almost bet is a Nassarius snail with a feather duster growing on its shell, i have about twenty in my tank they help stir my substrate and usually only come up when i feed, but then again they do what ever they feel to.
Rick got it right... assuming your sand came from Florida, Gulf of Merxico, or the Caribbean, the species is Fasciolaria tulipa.
As for the other guy... any pictures with more detail?
TJ have a look at the stomatella varia pic.