I just had my first encounter with planaria and used dog dewormer (I don't remember which brand) with fenbendezole in it. That's the important part. It came in 1 gram packets of powder. I read a couple of places to dose .1 gram per gallon. I just spilled the powder out and divided it up by sight. I took the carbon out of the filter and it has been two days with no planaria or hydra. If I don't see any planaria tomorrow I'll put the carbon back in and do a big water change.