For that I believe you would need to QT every fish for 6 weeks in treatment. Difficult if you don't have a big enough QT.
The idea is if you prevent it happening in the first place you should be fine. Not 100% but much better than risking it. A lot of people risk it and I'm one if them. I do however have a 70 litre QT ready if I need it with treatment at hand.
Current tank 260g FOWLR.
Fish: Moorish Idol, Powder Blue Tang, Hippo Tang, J Emperor Angel, 3 Chromis, 2 Black & White Clowns, Yellow Tang,