I just used it this weekend for the first time on my 180g. All went well, and I have what I feel like were a lot of them crawling around... I kept the skimmer and carbon running and dosed a little over the recommended amount. I also did about a 20% water change 2 hours after dosing. There did not appear to be any added fish stress present from the toxins. It has now been 2 days and I see no ill effects. I have some additional medication onhand in case they come back, but I would not hesitate to dose the tank again.
I had tried the six-line route and the mandarin route, but they either could not keep up with them, or did not have a taste for them because in the 4 months or so he was in there, the population did not see a decline. Just my personal experience.