Defective Nitrate test in API Master Kit?

I posted yesterday in the Water Change forum, about surprisingly high high nitrate levels in my tap water. I retested twice, and tested from different faucets, and even our filtered refrigerator dispenser’s water.

All tested at between 40 and 80 ppm.

(Our 10 gallon planted tank brings the level down to 20–per API kit—after about 24 hours.)

Before contacting our local water authority, i found a drinking water test kit we bought about 5 years ago, but never used. It uses strips, not liquid.

That test indicated the much more normal level of nitrates between 0 and 5 ppm.

What’s going on here? Has anyone had a defective API kit?

 

I would trust the kit over the strips, any day.

 

Maybe not exactly defective but if its been a while since your last test, you might have to really agitate bottle #2 to mix it back. Like shake the tar out of it for 5 minutes.

 

API test kits, especially the nitrate test kit, you have to follow the instructions e x a c t l y t o t h e l e t t e r. Like holidng the bottle vertical to ensure uniform drop size, and you have to time that sucker for thirty or sixty seconds or whatever it is (i'm not sure with the FW kit) or you won't get an accurate reading.

 

Thanks all. It’s just such a huge difference, and of course our local water authority lists our address’s nitrates at being under 10 ppm.

I test just about every day, and do follow the precise directions. I use my phone’s stopwatch to be sure. I even rinse the test tubes and cap in the aquarium water before filling them, to make sure there’s nothing else left in the bottle since rinsing under tap the day before.

I will shake the bottles for a full 5 minutes and see if that makes any difference.

 

will shake the bottles for a full 5 minutes and see if that makes any difference.

I suggest getting a new bottle entirely. API told me (when mine read wrong) that repeated improper use will change the composition of the liquid over time, so they sent me a new bottle and it worked.

I assume what happened was that sometimes a drop or two come out before the bottle is completely vertical, and over time it affected my readings.

 

How many fish are in the tank?

 

I assume what happened was that sometimes a drop or two come out before the bottle is completely vertical, and over time it affected my readings.

Ah, this could be! I let my daughter help a few times, and this definitely happened. I didn’t use the results when it happened, but it didn’t occur to me that it could mess up the concentration of what is in the solution itself.

 

How many fish are in the tank?

Hi Wrench. We have six zebra danios and one nerite snail.

 

If nitrate bottle #2 is actually a suspension then you need to use it quickly before all the solids settle again. Otherwise it's not much better than an unshaken bottle.

 

Hi Wrench. We have six zebra danios and one nerite snail.

well it's not a big bio load lol.
Have you tried cleaning gravel and decor?