I have a 180 gal mixed reef about a year old. I’ve been using GFO kind of blindly off and on for the last several months, I don’t use the GFO unless progress seems to slow down and it has always seemed to help my corals grow better again but I’ve read several horror stories about overuse of GFO so I shut if off when things look better. I have an API test kit and it always reads 0, I guess, pretty hard to tell with this test kit. I just got a Hanna Alk tester a couple of weeks ago and like the ease of use and that it gives a direct DKH reading. I’ve been thinking about getting a Hanna ULR tester but not sure if I should the Phosphate ULR checker or the Phosphorus ULR checker and convert the value to phosphate. The Phosphate ULR checker doesn’t have the rock solid reviews like the Alk checker does so I was wondering what you all thought about the Phosphate and Phosphorus ULR checkers and if one is more accurate than the other?