I have a 110 gallon fuge under my 125. I have the fuge on a reverse lighting cycle. My PH is consistent no matter when I test. I have tested at 3am and at 1pm...PH 8.2. Mine has 13+ types of macro, 120 lbs of live rock, 3" sand bed, brittle stars, blue linka star, serpent stars, cabbage leathers, gorgonias, anthelia, mushroom corals of all types and colors. I love my fuge. It is teeming with pods and critters.