Always restart your quarantine tank. It gets rid of any unknowns if something happens.
You might not be risking your main tank by reusing your QT tank but you risk the new fish going in it. A 10gal is super easy to clean and start fresh for new fish.
40Gal Planted- 10Gal RCS Planted
6 Julii corys, 1m Furcata Rainbows, 2f 1m Bose Rainbow, 2 mystery snail