Yes and No. IMO everything, fish, coral, inverts should be put in a QT. This will save you headaches in the future. That being said it depends on what you are trying to quarantine the fish for. If it is only for Ich and you already have fish in your tank that haven't been quarantined then it is most likely already in your tank and I wouldn't bother with a QT. If you keep losing fish in your QT you might be having ammonia spikes. Depending on how you have it set up you will need to do a combination of prime (ammonia remover) and water changes. I learned the hard way about quarantining everything and am doing it the right way now.