3-5 weeks. There's a slight risk of a small ammonia spike once you remove it from your established tank, so feed lightly check your levels for the first few days. I've not had an issue with this when seeding filters though. Unless your established tank is under filtered, you're basically stealing bacteria from the established tank.
I do find that the established bacteria is minimal, so the initial stocking should be low, but it will cycle a tank very quickly (a week depending on introduced stock.)