Nitrate testing ... Trouble with LaMotte Nitrate Test Kit 3110?

[Olliesshop]

I'm trying to determine why I seem to be getting false readings from my LaMotte Nitrate Test Kit 3110. I purchased the test kit a little over a month ago and have done 15 tests. The trouble I'm having, though, is the reading stays the same before and after my 30% water changes (2 ppm Nitrate Nitrogen, which converts to 8.8 ppm Nitrates if I'm doing the conversion correctly). I've contacted LaMotte directly and they were helpful at first, thinking the test chemicals might be outdated or contaminated. I gave him the lot numbers and haven't heard a peep since.

In my research it appeared to be the best Nitrate test kit available, so I'm a little frustrated.

Has anyone else run into this problem before or have any suggestions what could be going on?


FYI BTW, my water parameters are; 0 NH3, 0 Nitrite, Nitrate (0-8.8 ppm?), Alkalinity 10, pH 8.17, SG 1.025, Calcium 480-500, Phosphate 0 (Hanna), Magnesium 1388, Copper 0, Temp 77.5

 

[Dan_P]

Matching colors in colorimetric tests is not easy. Especially difficulti is trying to see a difference between 8 ppm and 6 ppm (expected reduction after a 30% water change).

To test your eye and the test kit, mix 1:1 tank water/new salt water and 1:4 tank water/new salt water. Test a sample from each dilution . The nitrate level should be 50% and 80%, respectively, of the tank reading. If you don't obtain these results, the new salt water has high nitrates, the kit is bad, or you might be color blind, or all of these.

 

[Olliesshop]

Thanks ... I'll give that a try.

 

[Olliesshop]

I ended up running 2 tests. The first one I ran with new saltwater to see if it would register anything and it was clear/0. The second one I ran 1:1 tank water/new salt water and got a reading of 1 or 4.4 ppm Nitrates, which is half of what I get with just tank water. So it looks like the test kit is accurate, which is great news! Although, I wish there were more gradients on the scale so I could see small changes better.

Now it's back to figuring out how to minimize the Nitrates. I think I'm going to have be patient and let the tank age more. We'll see.

Thanks again for the great suggestion!