I just recently had to upgrade my QT, Im in the large angel phase, and they're a delicate nightmare if not quarantined properly. I used to use a 15 gallon, which worked great until I wanted bigger fish. a 10 gallon works as long as theyre small fish being quarantined, obviously you wont put a 5" fish in a 10 gallon, it couldnt even turn around. However when I went shopping for my new QT I found the perfect deal at Petsmart, I got a 20 gallon long for 24.99 which hosted my 5 1/2" blueface angel for 3 weeks with no prob. I would reccomend a larger QT and for 25$ its def worth it, it costs about half of a fish, much better to be safe then sorry. But let me know what you end up doing, it is all based on opinion, but the point of a QT is to keep the newly STRESSED fish as comfortable as possible. So think about it