I also have a Mastertronic, Dosetronic, and Alktronic Pro. Top of the list as the worst, most expensive reefing equipment I have purchased. The Mastertronic always has an air leak in a dosing pump or syringe, the Alktronic killed my tank, and now won’t hold an accurate reading. I want to sell them and buy something else but it doesn't feel right passing on the problems to someone else. I also don’t know of an accurate phosphate tester as all I hear is bad things about the Trident NP phosphate accuracy.