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Inconsistent nitrate tests (both with API freshwater master)


Oreganoodle
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3 days ago or so I was about a week out from my last water change but also had a lot going on that night so decided just to test the nitrates to decide if the water change could wait. Got a reading between 10-20 on API freshwater master, and decided I could wait a few days. Fast forward to last night - I open a new testing kit b/c my last one was running low and I wasn't sure if it had 10 drops left in each bottle. 5 ppm.  I hadn't touched the water in between (not even a top-off).  I thought I must be tired/doing it wrong so I tested again -- same thing.  So I went to bed and then tested again today.  I used both tests this time (low-and-behold I did have 10 drops in the older kit). Sure enough - the kit I've been using for awhile says between 10-20  and the new kit says 5 ppm. 

The are both unexpired, and both the same exact brand. I've run the 5 ppm one three times total and it always is a very clear 5 ppm.

Which would you trust?

 

 

 

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On 7/21/2022 at 3:13 PM, Oreganoodle said:

3 days ago or so I was about a week out from my last water change but also had a lot going on that night so decided just to test the nitrates to decide if the water change could wait. Got a reading between 10-20 on API freshwater master, and decided I could wait a few days. Fast forward to last night - I open a new testing kit b/c my last one was running low and I wasn't sure if it had 10 drops left in each bottle. 5 ppm.  I hadn't touched the water in between (not even a top-off).  I thought I must be tired/doing it wrong so I tested again -- same thing.  So I went to bed and then tested again today.  I used both tests this time (low-and-behold I did have 10 drops in the older kit). Sure enough - the kit I've been using for awhile says between 10-20  and the new kit says 5 ppm. 

The are both unexpired, and both the same exact brand. I've run the 5 ppm one three times total and it always is a very clear 5 ppm.

Which would you trust?

 

 

 

I would trust the newer one. But....

I read somewhere, maybe here, that the #2 bottle can get thick or chunky or something. That's why you need to shake the crap out of it. Maybe one of those is that way?

But either way, 5 or 20 ppm is nothing to write home about anyway. 

Edited by Wrencher_Scott
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On 7/21/2022 at 6:59 PM, KBOzzie59 said:

do you shake the solution per the instructions?

Yes. 10 drops of #1 in, flip the tube once or twice; shake bottle #2 for 30 seconds; 10 drops of #2 in; shake tube for 1 min - wait 5 minutes then read ... every time.

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They are wildly inconsistent. I tested our RO water for giggles before it got tested by the company and it showed 15-20 nitrates. The RO company came back with 2 nitrates. 

Try mixing the old #1 with new #2 etc and see what you get.

 

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