About a month or so. Ended up using about 70% water from the big tank, moved all the live rock over, and added about 30% new water for a "water change" Let it sit for a wee bit...then added some fish / corals when the parameters were good for two weeks in a row. Glad I didn't post this pic 2 weeks ago, green algae was everywhere. Now I have the red that's coming and should be going shortly.