Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Are you using the estimative index? EI?
Are you dissolving the ferts in water then dosing the tank with the water?
a) Perhaps you measured the ferts wrong. (used tablespoons where the recipe calls for teaspoons?)
b) Perhaps you dosed the tank wrong.
c) Perhaps the test is wrong. I have a very hard time seeing the different colors once it passes 40ppm. Still, even 40ppm is a LOT.
Ways to check the test kit:
~Put just 1ml of aquarium water in the test tube, and add 4ml of distilled or reverse osmosis water. Then multiply the result by 5.
~Fill a 5 gallon bucket with tap water (as long as you know it has no NO3) (perhaps 4.5 gallons- since a 10 gallon tank does not hold 10 gallons) and dose 1/4 of the amount that you put in the tank. Stir well, then test. It should come out to 40ppm.
What I would do:
1) 2 x 50% water changes, then test NO3 again.
2) Not dose any more until the NO3 is well under 20ppm, and actually, I do not dose until it is down to about 5ppm.
What substrate are you using? Could it be producing ammonia? (Which is then converted to NO3)