...Almost forgot to state that personally, my preference from the start would be to get them in one of the bigger tanks, for me the ten would only be a staging tank, from an hour or two to a few days, how long depending on size. If the target tank would be the 55 (ich) I'd wait to order them until I was confident the tank was ich free, no sign of ich for at least 10-14 days. My opinion...
Unless they are tiny I can't imagine QT'ing them in a 10g tank. I would think you would need at least a 20L once they hit 3" or so.
..... or buy a larger QT tank.
Either way, always best to QT new fish in a tank designed for just that purpose.
If it was me, I would be keeping them in the 75 more than a week ....