I have gone to quarantining all fish after the dreaded WS. I have a 63 litre jewel tank with sponges 3/4 fish at a time I simply add Seachem Paraguard at a set dose daily at the same time from day one for 3/4 weeks. It is a broad spectrum medication and treats other problems, It dissipates from the water column after 24 hours hence the daily dose, after the 3/4 weeks leave for 24 hours the water is free of medication then add fish to DT. For me a couple of advantages of Paraguard is that I can do a water change at tea time (the time I medicate) then simply add the meds no need to test to keep levels correct like copper, also no contamination of equipment. In the five runs I have done two lots showed signs of WS after 2/3 days then disappeared, just shows why we should quarantine. I have cleaned the inside of my DT several times chasing the fish around the tank with no signs of WS.