Nitrate Test Kit Questions

[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

 

[Silly me]

first of.. there will alays be some algae i a planted tank.. You'll need a SAE or five to prevent a outbreak if something go wrong and to remove most algae when they appear.

I add KNO3 to my tank to till I get a Nitrate reading of 10ppm, at waterchanges it like 15drops and every second day I add about 1-2 drops

so a very low reading in a planted tank is possible, my test kit just shows >10 - 10-15 - 15-20 - bla bla bla <100

 

[Bol]

Nexstar,

The difference in readings (of a factor of 4.4) between tests isn't because of accuracy, it's because they're two different types of tests -- i.e., they measure two different things.

There are two main types of nitrate tests out there: one measures the concentration of nitrate ions (like the AP test kit does), the other measures "nitrates as nitrogen" -- that is, the amount of nitrogen in the total nitrates. The conversion factor between the two is (NO3-N)x4.4 = NO3-.

This article by Novalek probably explains it better than I did.

A second nitrate test as a check is never a bad idea. and I've heard good things about the Seachem nitrate test.

On a side note, another secondhand opinion ... many plant enthusiasts consider the available iron tests to be terribly inaccurate, and generally a waste of money.

 

[luxum]

My nitrate test (AP dry tab) only reads 0-20 as the lowest reading, then goes up to crazy 100ppm or so. Hence, my nitrates always read zero or unmeasurable... anyone recommend a good test kit with a lower test range?