I don't test for phosphate since I am not running reef tanks and I simply use nitrate as an indicator of other pollutants. The reactor has been tested across two tanks. The reason I tested two tanks is because the first tank houses a peacock mantis shrimp only and the foods he eats (live crabs, clams, frozen food soaked in selcon) might be lacking the necessary levels of phostphate that a prepared fish food might have. So, I moved the reactor to a fowler tank containing a melanurus wrasse, royal gramma, damsel, and a havanensis mantis shrimp. Same outcome.
One thing that I am thinking about in hindsight... Maybe my light strip really was running brighter than everyone elses? There is no power brick to regulate that so maybe the voltage was higher from my wall than it needed to be.
Also it is a rather small reactor and the lightstrip would sometimes sag and create a higher density wrap towards the bottom of the tube. Maybe all that light in one area contributed to the issue occasionally.
Maybe both? I do not know.