Hanna phosphorus kit Hi736...testing question

[miserkris]

Yes, full strength. Yes, I have RODI on tap. Not terribly sure it would be worth it if not easy though.

Do u actually sit the vinegar for few mins in the tested vial or just rinse thoroughly and then do same thing with rodi?

Wonder if it's best to let vinegar clean for a while and leave no trace.

 

[miserkris]

Guys. ...I've been testing phosphorus every week using hi736. It ranges from 9-15[phosphorus ].
My mixed reef looks great now.

Question is how low is dangerously low when it comes to phosphorus reading using this method? I'm asking because some corals do need phosphorus i mean phosphate for survival right? Thanks