i just quit checking for phos, i run gfo so the way i see it is if they are there then im not gonna add anything else so i just change my gfo every 6 wks.
since i have no algae besides some film on the glass im assuming they are absorbed or used up through my fuge in either case im happy.
nitrates is a diff story i do nothing for them so they go up and down
__________________
........
|