I'm going through the same thing right now I'm still feeding the same but doing a 10-15% water change everyday and getting every last spec of debris out once a day it seems to be working. I read about this meathod I read about a trap you can make at home to catch some of the planaria. Take a small plastic container with a lid, cut some holes in it large enough for the planaria to crawl in, bait it with something meaty, set it inside another larger container without a cover and wait overnight. Use some gravel to weight down the container. The worms will crawl in to eat the bait and you can scoop out the container and kill them with bleach or hot water. The second container is to catch any of the worms that fall through the holes when removing the containers from the tank. It's supposed to work pretty well.