I’ve been struggling to get wrasses through my QT process… a six line made it but was subsequently killed by something in my tank. I assumed Cooper could be an issue so I stopped that with all wrasses. Then a blue throated wrasse made it through QT but died in my display. He was never treated with copper - observation only. I have a new wrasse in QT now (observation only). It stopped eating or moving and will likely not make it. I’m about ready to give up on having a wrasse in my tank. My QT tank is ten gallons and I change five gallons per week. I have a hang on back carbon filter. Has anyone else had a difficult time QT’ing wrasses? Maybe I should just purchase one already QT’d. Given the money I’ve wasted it’s probably the smartest approach.