FYI, hydra can be very difficult to remove. They have a 'root' that goes in the shell, and are best removed once the infected crustacean molts. The best way to get rid of the parasite is to remove the discarded shell immediately after it molts, and before the parasite has a chance to move to reinfest it's host.
Well, this one wasn't hard at all. Used the regular turkey baster, comes off with little effort. No visible mark where it once was.