I am using formalin as a long term bath as suggested by some friends who are importers and deal with it frequently. I am adding formalin to my 20 gallon quarantine tank daily at night right after doing a 25 percent water change. I have been adding 1ml of formalin. In the mornings I have been adding 5ml of paraguard. The brook does not seem to be getting any worst but does not seem to be going away either. Last night I bumped the formalin up to 1.5ml. I will see tonight if that seemed to make a difference.