i have the same problem. I have tried to suck as much as I can each water change but they reproduce too fast. I heard spotted mandarins do pick at them. So, I got one but I don't see them eating the flatworms at all. I guess it is a hit or miss thing. I also was told that melanurus wrasse or other types of wrasse do eat them. I think I'm giving up on the idea of having a livestock take care of this problem. I am going to bring out the big guns and will be using salifert flatworm exit. LMK if you want to split the cost because I heard you don't need to use alot and it cost like 20 bucks.