I don't know why Formalin is so hard to get lately. I even think some states have banned it. there are a few products that contain fomeldahyde, the ingredient in Formalin, but there is still the QT issue. I hope these fish don't give brooklynella to all your fish. They are probably tank-bred; so much for the myth that tank-bred clowns are immune to brook. When you recover from this, please QT EVERYTHING wet and you'll never go through this again.
If you want to keep a small QT/HT set up; here's a copy of how I instantly cycle mine.
"In regards to Qt cycling; I've done this for years. Get a HOB filter; I really like Aqua-Clear, they have a big sponge and last forever. Don't use the carbon or ceramic noodles that come with the filter. Also, have some extra sponges on hand, they're cheap. Keep a sponge in the flow somewhere in your DT. When you need a QT or HT, just use the sponge that has been in your main system in your QT filter---the QT will be instantly cycled. When done, toss the sponge and keep a new one ready in your main system.
BTW, Cupramine copper, used in a QT,will not destroy a bio-filter."