Is it possible?
Athoug I use Fr, although I use rowa phos, although I change water, althoug i use skimmer its still 0.5 no matter how.
when i change water, and measure the next hour, the reading will be zero or o.1 but after 1 or 2 days it shoot up again to 0.5 or sometime even 1. THis has been happening for the last 1 month.