Well, in a sense it's bad because enough of them will prey on your pacman - even the babies when they're hungry. So I would either try to remove all the soil coming from where they hatched or just clean out the whole tank and start over. Without food and water they should die within a couple of days or all the way up into a week, but I wouldn't risk it.

Did you notice that there were a lot of them in there? If you don't have time right now to clean out the tank until a later time, leave a carrot or some type of vegetable in there. Keep the soil moist so they can stay hydrated.