NT Labs nitrate test stopped working.

[Maff]

Here's the situation. I have NT Labs test tube kit for ammonia, nitrite and nitrate. All was working 100% then the nitrate test has stopped working. My tap water contains 9.7ppm nitrates which it was picking up before and it picked up my tank nitrates as high as 20ppm. We've noticed lately a brown algae bloom appearing on the substrate and lower regions of the glass. Yesterday the nitrates were showing 15ppm and I did another test this morning and strangely it showed 0ppm which I thought was odd. So I tested my tap water which is also showing 0ppm. It's impossible to have 0ppm nitrates in a tank which has a brown algae bloom gathering pace rapidly.
Now I don't know what my nitrate readings are.
Anyone else had a similar issue? Maybe my water company has done something to my water which is nullifying tests?

 

[Maff]

Right, I've worked out the problem here. Because I don't use the nitrate test reagent as often as the other two, it drops out of solution and settles at the bottle of the two bottles. The instructions tell you to shake for 30 seconds while its upside down until you can no longer see sediment at the bottom. I was shaking and not checking the sediment as per instructed on the box. The box just says shake for 30 seconds but doesn't tell you to check that the sediment has dispersed. The box tells you to shake the test tube vigorously but not for how long and neither does the instructions. I shook for about 15 seconds which isn't enough.
I went online and found an article about it. They said you need to shake the test tube for 60 seconds after you make sure you've put the reagent back into solution in the two bottles. I checked my bottles and sediment was still stuck to the bottom. In other words I've been performing inconsistent nitrate tests right from the very beginning of the new tank and my nitrates were probably higher than my tests indicated.
Just done another test and I'm at 20ppm and ready for another PWC.
So a bit of advice for anyone using NT Labs nitrate test kits. When you shake the bottles you might need to shake for more than 30 seconds to get the sediment back in solution and you must shake the test tube for a minimum of 60 seconds.

 

[PheonixKingZ]

Glad you figured it out.

Make sure to follow the instructions exactly next time, to get the proper results.

 

[Slaphppy7]

Same thing with the nitrAte test when using this kit: https://apifishcare.com/product/freshwater-master-test-kit

 

[Essjay]

My tap water contains 9.7ppm ammonia

I hope you meant 9.7 ppm nitrate


(The maximum ammonia allowed in tap water is 0.5 ppm)

 

[Maff]

I hope you meant 9.7 ppm nitrate


(The maximum ammonia allowed in tap water is 0.5 ppm)

Amended, I meant nitrates. The only ammonia present is after you treat with prime and the chloramine releases small amounts of ammonia.