people really need to read the entire post... Levamisole is extremely rough on fish and those that are sensitive normally do not do very well. It definitely does not work that fast as far as the treatment because the treatment is over a 3 to 4 day period. It takes effect fast and you can often see worms being discharged within the first hour, but pending the parasite, it may take awhile. It will kill off shrimp and snails as it killed both in my tank.
Completely agreed. I have seen people say they did water changes after 24 hours, and I would have to say that isn't nearly long enough to guarantee the treatment successful. I treated a rainbow shark, and while he seemed the least affected by the levamisol over the 3 days, the second I dosed that tank I could just see him goin crazy and thinking WTFFFFF? Really odd behavior over those 3 days.
Levamisol is no fun. It's painful to watch your fish living in what must be a really harsh environment.