so i tried using fenbendezole (or however its spelled), but i doesed it for two days now, and wondering how often i should do it along with how much/ how often i should be changing the water. Another thing, what should i expect, i have crs and i don't want to harm them. SHould i expect the planaria to start appearing and dying or what? they're pretty scarce and only see them a few at a time, but i want to get rid of them all together. so how do i know if im successful as they're all in the substrate.