Ich could easily have been in your tank and the Hippo just got it there. No LFS does a decent QT regimen and you should assume all new fish have ich or other parasites. A QT does a lot more than just catch ich and other deadly parasites. Fish adapt to captivity and their diet much easier; there is no bullying, competition, or general mayhem. Because your whole system has ich, all fish need to be treated and the nDT left fishless for 10+ weeks. There just isn't an easier way. Your QT size will depend on how many fish you need to keep for the 19 weeks. A tank, heater, some PVC pieces for shelter and patience are all you really need. Craigslist is a great place to find a QT; at least, everything but the patience. You can move the UV to the HT, it will help a little. Cupramine and a SeaChem copper test kit would be my choice. A HOB filter, I really like Aqua-Clear will help hold aerobic bacteria and also help keep the surface for gas exchange. Assuming you don't have any well-seeded filter media in your DT; Dr. Tims or Bio-Spira will help get your bio-filter started. Ammonia is an enemy in a HT if you're not ready. Get a SeaChem stick-on Ammonia Alert, regular ammonia tests don't work with copper. Ask a lot of questions as you go. This is going to be a big PITA, but use a good QT on all new fish from now on and you'll never go through this again.