When it comes to clowns it's usually best to have just one pair per tank. I had 2 b&w's and 2 oscellaris in my tank. it was all fine for months, they even all slept together at night. The one day the female osceallris just decided it was time to kill the b&w's. It was really really brutal and luckily I got them out that night and saved them.
To my knowledge all fish can be treated with Hypo. If you do set up that 50g as a QT you only need a heater, a small filter and some PVC
pripes for the fish to hide in so they feel safe and dont get more stressed. You don't need powerheads or skimmers. You will have to monitor the water parameters and do water changes when needed. it's a long process but it will work in the end, and really is the only known way to be sure its gone.