Ahkay, I have a bunch of platies and some cories in a tank. Well, today I noticed one of the female platies (full grown but not colored) had a few parasites on the tail. Well I go to look at the medication that I have, and uh oh, I have a dilema.

"Do not use with invertibrates"

I have a bunch of snails in the tank too, but I dont want them to die!

So what should I do?

You will have to move the snails and the corys out. The corys for some reason are mostly resiliant to ich but not the meds.
I would use salt rather than the meds any way, but again you would need to move the snails and corys.