Hello. I kinda let things go and will soon be rebuilding my 20 gallon high. It's presently a dirted tank and I plan to use this method again. I plan to move my angelfish and my corydora to a 10 gallon for the rebuild. My plan is to use my existing water, split between the rebuild and the 10 gallon since it has established bacteria. I plan on getting the rebuild done in 6-8 hours. How long should I wait before moving my fish back into the 20 gallon tank?