Treating multiple big fish with velvet

[Coralvol]

Hello all, took the gamble and did not QT. I currently have all the signs of velvet. ( standing in flow of power head, covered in white spots, hiding from light ). My question is I know I need to move them to a QT but wouldnt 10-20gal tank cause a mass ammonia spike and kill the fish anyways ? I could take a piece of live rock from my sump and add it to the QT and throw it away after but idk if that will help my cause. I have noticed the Kole tang covered in spots for a couple days and now all fish covered but still eating. I have a 55wt UV sterilizer and dosing H202 (1ml per 10gals) today to see if there are any changes by morning. Tank is 165 gal.

Currently stocking list below.

hippo tang 3 inches
Yellow tang 5+ inches
Fox face 4 inches
2 clowns
Diamond goby
Filefish
Kole tang 4 inches
Blue damsal

 

[Big G]

A 40 breeder would give you a lot more room and water, but not too big to make treatment difficult (water changes) and costly.