Unfortunately if they were together,chances are your tank has ich and also needs to be dealt with.
I have qa 10 gal tank you can use,unfortunately I do not have a QT tank set up at the moment as I wasn't planning on getting any fish.
If you don't have an extra tank, you could go out and buy a rubbermaid tub or a 10gal tank from petmart/petco for $10. That way you could treat your clowns and any other future fish you get.
If there is not a host for it. It will die off if all fish are removed that way it doesn't have a host to be on. The eggs will be in your tank and will hatch, If they don't find a host they die off. You need to give it 60 days without anything to host on to clear tank of it.The 60 days is up for discussion but i never rush back in.