Manual removal has worked well for me, you need to be very persistant. Siphon them out as often as you see one. At first it will seem like there is no end but eventually you will notice fewer and fewer until you hardly see them anymore. Not a cure but you can easily control them. Once you get them to an extremely low population then if you want you could use the Flatworm exit. I dont use it cause it didnt work for me I still had some left after treatment, plus the FWE along with toxins exuded by the dying flatworms can and will harm other invertebrates in the system.