I know it is a controversial topic. I choose to treat prophylactically. Wrasse unfortunately, are really good at harboring things such as ich, velvet, flukes, etc. without any visual symptoms/behaviors. I have 4 in QT right now from LA. Leopard Female, Black leopard, Exquisite fairy, and a McCoskers. 4th day of therapeutic copper and doing well. I did start with two bluestars that didn't make it past the first 48 hours in my tank, due to shipping stress. I am using copper power. (I waited 7 days after they were all eating well, to begin copper, and spent 6 days ramping up to my target level of 1.75ppm)