I recently found one living in my under gravel filter! Pulled off an uplift tube to clean it and it swam out from under the bottom plate. Far too big to get out on its own. Must have gone through the outlet while still small and grown up in there in the dark
I'd make sure to do some real good gravel vac between treatments to make sure any worms are removed. I'd also look at a levamisole treatment if you found worms.
Hi, glad to be here, from Sydney. I'm looking forward to being able to buy aquarium coop products in Aus some time soon! I'm breeding rainbows, bristlenose and Corys.