*sigh*
I'm so sorry to hear about this. Geez, I hate these chemicals.
Sorry about yours too @yellojello . So sad.
It's not the chemical it's the amount of flat worms in his tank. It sucks but eventually things will crash cause of the sheer amount of flat worms that's in the system. I really don't know how you can keep that in check except for having a predator that eats them.