Velvet ?

[Dive_dry]

So I had velvet go through my tank last week I have 2 fish left and it looks like 1 of them has it to.How long should I let my tank sit before adding any new live stock as I don't want it to return
My fish list was
Powder brown tang
Sailfin tang on its way out
2 ocellars clown's
Bangi cardinal
Coral beauty
Alge Benny
4 green crosmis I believe the culprit

Yellow tang still healthy