I thought I would update the progress with my de-hydra-ation experement.
So far the small tank, which is my 5.5 gallon, and prolly got a bit more than 0.05 grams of the medication is free of living hydra. The Macrobrachium Pilimanus in there is doing well.
The Main tank, 25 gallon, I used 0.15 grams of panacur. Planaria are upset for sure, I've seen them moving around for the first time in months. There are still hydra but they don't look very happy.
All other animals seem quite happy.