A good gravel vac might get some of them, once you get fish in, they will eat some too, they mainly stay in the gravel I believe, come out at feeding time.
Id personally leave the planaria in there unless you are really over-run or get them all over the glass. They are great snacks for small fish, and if you stock the tank with anything kind enough to breed for you then the fry will certainly enjoy the easy meal.
