Anchor worms have a paired breathing tube at one end and a little pointed lump at the other, if they are anchor worms dump your substrate until you can bleach and rinse it, then do three consecutive daily 50+% water changes while warming and salting the tank like you would for ich. If any have dug into your fish they can be manually removed with a pair of tweezers and a steady, gentle, straight out pull. I have never seen a heavy infestation like you describe, only one or two on newly acquired eels and native cats. I have seen a swarm of white worms show up out of a disturbed biofilter medium in a community tank. My pristellas ate most of them and the salt routine killed the rest.