I use 2 QTs: a permanent (cycled) 20 gal with sand, live rock, good lighting, canister filter (carbon only), PVC pieces, and decent water flow. All new fish go in this tank for 6 weeks. If a fish develops a problem I set up a 10 gal BB with power filter and PVC. I treat with hyposalinity and or copper depending on the fish.
This way a perfectly healthy fish need not undergo treatment, and I can QT inverts in the 20 gal and not worry about copper in the tank.

This is a great way go. If I had the room, I would also keep a QT always up and running for everything new I buy but its just not possible right now. For now its going to be a few months of QT and then nothing added to this tank! I am going to add the last two fish to the tank after this QT, so QTing new fish will not be an issue but I think I will need to set up a small coral/invert QT tank. I don't want to take any more chances in the future. Im heartbroken to see my puffers like this... :(

Thanks...It will work out, they are tough fish and the ich is very mild. Im just really mad that I let my guard down with this new addition. Before this, all fish had been QT'd for at least 6 weeks. All that work for nothing!!!

That's too bad.

I would suggest a NH3 test kit. It's amazing how fast it can build up to deadly levels.

I did the very same thing. A new fish that I was sure was clean wasn't. Infected another fish in the display and I had to QT the whole bunch. 8 weeks looking at an empty display really sucks. Good luck!

Yeah I have one...this is another must with a QT. I test ammonia, nitrite and PH twice daily during QT and more if the fish look stressed. I do use amquel though which can screw up ammonia readings a bit.