Hi Everyone, I have few question about ich/velvet treatment. Well, I decided to add a powder blue tang to my tank that already had 12 fish( yellow tang, clown, puffer, damsel, buttefly, angelfish). I got the fish from a reliable source that quarantine the fish 2 weeks already but still I quarantine 5 more days in QT and used Cuparamine to make sure everything is fine. But after I added him to the DT, after few days everything messed up and my tank wiped out. 10 fish died and I could see white spot and cloudy eyes on them. Just 2 clown fish and a damsel survived! Now I have few question: 1- what did go wrong? was it the blue tang problem? or maybe I already had some not noticeable ich before and adding the powder blue tang made it worst? I say that because I saw a little bit of white spot on my yellow tang before but it went away by itself. I did not know even if it is small sand sticking on him or not. 2- My more important question is that what should I do with these two clowns/ damsel? In the time that my DT wiped out I could see white spot and cloudy eyes on them but after couple of weeks it went away and they happily swimming around and are so active. I moved them to the QT to keep my DT fishless for 6 weeks to get rid of ich but still in QT they are also happy and no spot at all. Is it possible that they carry ich but it is hidden? If it is the case how can I trust buying any fish and QT that? It might have it and does not show for couple of weeks in QT and later transfer it to a more sensitive fish like powder blue and thing go wrong again?