Nitrate test kit
First, a little background. I started dosing EI back in November. In December I added Discus to the tank. Since the Discus experts always preach about the need to have low nitrates, I got an AP nitrate test kit. When I tested the tank water I was shocked to find that the test kit registered a number I couldn't read. It was somewhere around 80 or more.
I tested my tap water that I use for water changes and got a reading of 10. At that point I figured the heavy feeding and tap water were enough to maintain nitrates and stopped dosing KNO3. Ever since my tank has always tested out to 10. L repens wasn't really red, and I attributed that to the fact that I couldn't get nitrates lower.
I started getting fuzz algae, and then noticed some BBA. The Excel overdose treatment got rid of it, but the fuzz came back as soon as the treatment was stopped. All this time I kept cranking up the CO2 but that didn't help.
Finally, I decided to test my test kits. Everything tested correctly - PH, KH, GH, N, and P. Since I was still dosing KH2PO4 and K2SO4 at good levels, I decided to add enough KNO3 to bump it up by 5ppm, figuring that would take the tank to 15. It didn't, the test kit still read 10.
All this has me believing that something in my water is tricking the test kit to read 10 when it is something much less. I am going to slowly increase the KNO3 dosing to see what happens to the readings, but the effects are already apparent. The algae seems to be melting and the L repens is turning red after one day.
Any thoughts on what the source of the false reading could be?