Life of water testing kits?

I have read through a few of the threads on Fishlore regarding water testing kits, but have not found an snwer for my question.

I have been testing for nitrates in my tanks recently, as I had a bio overload due to guppy proliferation. I have taken care of the abundance of gups, but am now monitoring my tanks weekly to get water levels back to healthy numbers.
I have been using the API Freshwater Master Test Kit, and the nitrate results are coming out dangerously high, however when I test with the API test strip, I am getting results showing the nitrates are safe. The expiration on the Nitrate solution bottles are 12/2024 and 01/2025. I tested the double filtered water I have been using, and that came back with moderate nitrates, but again with the strips, showing no nitrates.

Could it be possible the Nitrate solution has gone bad even though the expiration date is a few years away? I ordered a brand new API Freshwater Master Test Kit just in case it has. Is there something else that could be causing this discrepancy between the test results?
The test on the left is from my 10 gal, the one in the middle is from the double filtered water, and the one on the right is from my 30 gal standard. The top square on the test strip is the one that shows the Nitrate levels.

 

You really need to shake the heck out of the nitrate bottles. Even bang it a couple times to loosen the liquid up. But it could go bad or get a bad batch I imagine.

 

You really need to shake the heck out of the nitrate bottles. Even bang it a couple times to loosen the liquid up. But it could go bad or get a bad batch I imagine.

I shake it for the 30 seconds it says too, but I will try the banging part to loosen up whatever may be stuck on the bottom. Thanks!

 

Test strips are known to be inaccurate for the most part. The liquid test kit from API is the most accurate- so those results should be correct. Maybe get your water tested at a LFS and see if they have the same results as you? (Make sure they use the liquid test kit as well)

 

If you haven’t been mixing Nitrate solution #2 enough then it’s possible that the concentration is off thus affecting your results.
I would purchase a new nitrate test and compare.

 

Test strips are known to be inaccurate for the most part.

Several manufacturers, like API, produce low quality test strips to entice people to buy the liquid test kit.
There are good ones explicitly for aquarium use, that are not bad at all.

Problem is most often user error, though. Handling can be finnicky, water on the test fields should never mix. That's all there is.

Otherwise the accuracy of the scales of both types of tests is the same or near same. Still both can be off miles, when compared to a laboratory.

 

If you haven’t been mixing Nitrate solution #2 enough then it’s possible that the concentration is off thus affecting your results.
I would purchase a new nitrate test and compare.

Thank you for your response. I have purchased a new testing kit, it will be here in a few days. I'm glad to hear this is what other would do as well.

Several manufacturers, like API, produce low quality test strips to entice people to buy the liquid test kit.
There are good ones explicitly for aquarium use, that are not bad at all.

Problem is most often user error, though. Handling can be finnicky, water on the test fields should never mix. That's all there is.

Otherwise the accuracy of the scales of both types of tests is the same or near same. Still both can be off miles, when compared to a laboratory.

I have heard the test strips are not nearly as accurate, but the results are like night and day between the two types of testing. I will test again when the new Master Test Kit gets here.

You really need to shake the heck out of the nitrate bottles. Even bang it a couple times to loosen the liquid up. But it could go bad or get a bad batch I imagine.

Something else I just thought about, I have been using the Seashem water conditioner in the new water with water changes, can that cause an inaccurate reading in the nitrate test?