I did have some ph swings but I attribute that mainly to topping off with a small Kalkenstien. I now have a DIY kalkenstein that is 5 foot tall and 4 inches in diameter. I am using a quite one 4000 as the recirc pump. since making the switch I have not had any problems. I had never heard of a skimmer causing a ph swing how does that work as I am still somewhat new to the hobby and still learning. Thanks again to Joe Ayers he helped me build the new DIY kalkenstien.