Nitrate Test Kit Question

[nexstar]

I have been testing my planted tanks Nitrate because I have a Hair Algae problem right now and am trying to locate the problem.
I am using a Aquarium Pharmacuticals Test kit. It says that readings from other test kits will be 4.4 times lower than theirs. Further it states that a level of 40ppm or less is the target for a fish tank. I have a planted community tank. If that is true then my readings of 20ppm with this kit would indicate that if most others hobbiests are using Seachem or another kit and they are indicating 4.4 times less then th AP kit I could actually have 5ppm by the standards of these other kits. This concerns me because I need accuracy. If the Seachem kit is more accurate and reads lower then Nitrates could be too low and that could be a problem.
Other parameters appear solid
Ph constant 6.7 with CO2 injection with 3.7w per gallon of compact flourescents 11 hours a day. Plants are growing even glosso but this black hair algae is triving also.
I am doing daily 20% water changes with RO to preclude bringing in phosphates etc that could spur the algae even more.
Kh 4
Gh 5
temp 82 I live in So Cal and really tough to keep it in the 70's during the summer months.

Question is am I correct to assume that the real reading is more like 5 ppm or should I get a seachem kit. I am about to order the seachem nitrogen, iron, phosphate kits. Plus Fourish Iron, Flourish, Equilibrium, Flourish Nitrogen and Flourish Phosphate. Any other micro or macro ferts that I need.

Thanks
Bob

[teedee]

Hi Bob,

The difference you mention, the factor of 4.4, originates from some kits reading Nitrate (NO3) and some reading "Nitrate Nitrogen" (N). NO3 has a molecular weight of 62 (3*16 for O + 14 for N) and nitrogen has an atomic weight of 14. Hence you have to divide the number for Nitrate by 4.4 to convert to "Nitrate Nitrogen". However, the Aquarium Pharmaceuticals kit (I use the same) reads NO3 (Nitrate) in ppm which is exactly what you want. Most people recommend to mantain 5-10 ppm NO3 for a planted tank (either via the natural "production" by your fish or by dosing KNO3).

Ciao
TD

[malkore]

great explanation teedee.

a little more info: 40ppm in an unplanted tank is ok because nitrate isnt' terribly toxic, and a non-planted tank would have under 1 watt per gallon of lighting. No enough light for algae to bloom into greenwater.

Now, if you're having hair algae issues, look at high phosphates as a cause, rather than nitrates.