Planted Tank Enthusiast
Join Date: Feb 2011
Location: Hong Kong/Dallas, TX
When I had planaria(such a nasty worm), my fish would not touch them. I'd catch a planaria with a tweezer, drop it in a shoal of fish, and none of the fish (ember tetra, cardinals, CPDs, dwarf pencilfish) would touch it. Some would swim close to it, put their mouths right to it, and quickly swim away. Some people say there is a toxic slime that coats the worm. I would believe that since my fish eat everything else including nematodes.
Feeding less will definitely reduce it, if you are really impatient and want to knock them up, put some dewormer medicine in the tank, and you won't see planaria again. I left a specific amount of flubendazole (deworming medicine for humans) in the the tank a few days, haven't seen planaria since.