Is the blue hippo the only fish showing signs of ich? How long have the spots been on him? My blue hippo tang had ich. Used the Ich Attack as instructed. After the treatment, started adding Seachem Garlic Guard and Metronidazole to the food. It's been over 5 weeks, and no sign of ich in my tank. My puffer and green chromis never got it. My tang hasn't looked any better, and eats like a pig. I know everyone here jumps in an says QT, QT. But there are alternatives. It just depends how soon you start treatment, and what stage the ich is in.
You just need to decide what's best for your situation. I have read the posts here of people who got ich on one of their fish, and in a few days, all their fish had it. Many lost every fish they had to ich because they didn't treat it fast enough. The big debate is how to effectively treat each case of ich. Yes, hypo is the defacto method that has shown the most success. But is it absolutely necessary in every case of ich? As in my case, no. I had one fish get it (Mr. Tang the Ich Magnet), and decided to try the alternative methods. For me, it worked just fine. That may not be true for you. Again, you have to access how bad the ich is, and whether it's spreading to your other fish. Treat appropriately.
Do you have a QT tank already setup to do the hypo treatment? If you don't, you also have to deal with buying another tank, and cycling it. You can't just fill it up with water, put a heater in it, and move your fish into it. Like any other new tank, it has to go through the cycling process. You can try seeding it with bacteria from your DT (a used filter media out of your main pump, if you have one), but you will have to deal with the nitrate and ammonia spikes. Don't monitor the levels closely, and that alone can kill all your fish. Depending on how many total fish you have to QT, and how big your QT tank is, you also may be doing alot of water changes to keep the ammonia levels down. And you have to do all these water changes while maintaing a perfect 1.009 salinity level for three weeks. Oh yeah, rememeber you have to fork out at least another $40 for a refractometer to accurately monitor your SG levels while in hypo. That plastic hydrometer won't cut it.