You want to put the oscar in the 10 for while you move the 75, right? How big is the oscar? Why don't you just fill the 10g with used water from the 75? If you're asking how long to cycle the 75 after you set it back up, I would think it will be fine as soon as you fill it back up since you are using 50% old water. Just make sure you remove the chlorine if it is in your tap water.
Also how long do you think it will take to move the 75, depending on the size of the oscar I wouldn't leave it in the 10g for more than a day or 2.