Planarias should have come with a plant or something else introduced in the tank, and not cleaned enough. In my case, I remarked the planarias several days after I introduced catappa leaves in the tank. Now, not only I wash carefully the leaves, but I also "cook" them in the microwave. As I said, I succesfully got rid of this pest using dewormer. Not sure you can find Fluvermal in your location - this is a french product - but some use No-Planaria, or pet dewormer. See there: http://www.planetinverts.com/killing_planaria_and_hydra.html If you have snails and love them, be aware that the treatment may kill them too. Hope that helps ;)