id just say as well that when using that med make sure your oxygenation is turned up ive read quite a few instances when peoples fish seemed to be up the top of their tank gulping looking o2 starved shortly after they added No 8 med.
we had a nasty experience with the stuff a few years ago - it zonked out our tiger barbs completely, they were asleep for 4 days, we thought we'd killed them but after 4 days they started waking up for a few mins before going back to sleep ( nose down out cold!!!!) we had done loads of little water changes after noticing what had happened in a panic & there was definitely nothing wrong with our water params at the time either. none of the other fish in our tank were affected at the time although we didnt have our loaches then.
i did a bit of research on the ingredient that is actually used in interpet fungus & finrot med & it used to be used a a fish anaesthetic so it was pretty obvious what had happened to our barbs so id just be careful with the stuff
saying that it did cure the bad case of finrot that one of the barbs had but gave us a bit of a scare( all the barbs survived their big snooze with seemingly no ill effects!!!)