I want to go from a 20 gallon 2 part sump to a 30 gallon 3 section sump with a refugium in the center. Plz give me some tips on how to switch with the least amount of Bio problems. I have about 1 to 2 inches of crushed corral on drain side of 20 gallon but purchased 2 bags of aragonite sand. Do I just use new sand or a combo of sand and crushed corral out of existing sump. Tank has been up 6 mths plz give me suggestions on safest way to make transition. Thanks