I have never quarantined and then I got my little tang who developed black ich (flukes and 2 full treatment (4 doses) rounds of prazipro in my display tank and it came back after each treatment. My other fish (clown/mandarins) were fine. The 3rd time it started coming back again I tore apart my tank to catch it, totally stressed it out and put it in my new QT tank. He’s an Oscar worthy actor - He was stressed the entire time. Just laid on it’s side hiding under the pvc pipe. I had to pipette feed it. It wouldn’t swim and feed. Barely ate. I felt so guilty, and woke up every morning expecting to find him dead. After 12 days. I hoped I broke the flukes lifecycle in my DT and broke down and put him back in there. He perked right up, practically high-fived his clown fish buddies and swam around and ate like he never missed a day. it’s been a couple days. He seems all good. No signs of flukes yet. Fingers crossed. I’m torn on the QT as well. I just got some biota fish and didn’t QT thinking there’s a lower chance of disease direct from the breeder. I’m about done stocking my tank with fish. So hopefully I continue to dodge bullets with my remaining couple I want to get.