Common thought it change water after 3 days but if you have a bad infestation, I would change it after 24 hours due to ammonia spikes from dead worms.@randyl Do you have any suggestions around how long to wait after treatement/water changes before I'd want to reintroduce my rabbit snails if I went the fenbendazole route?
EDIT: I'm guessing I could just try reintroducing a couple of pond snails before I try the rabbit snails.
Panacur is not active in your water after 24 hours so you are not removing the medication.
If you scroll down on this page there is a good article about treating planaria with panacur http://www.planetinverts.com/killing_planaria_and_hydra.html