Several water changes for certain. to be cautious, i would add some small pond snails to test the waters.
Thank you Liam, I wasn’t sure if carbon would work on Zero Planaria I know it works for most meds. I will wait and do 2-3 water changes and add active carbon for a day before I throw the snails back in.run carbon in your filter for a day, then a good vacuum of moss if you can, in case there's some leftovers