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API Test Kit Nitrate Inaccuracy


ChrisD
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50 minutes ago, Kat_Rigel said:

I've had issues with the nitrate test accuracy, but its usually a higher reading than the true value.

I always hear about the liquid being inaccurate even when you shake the heck out of it, but the problem is neither test (strips or liquid) is super exact (honestly, 10 vs 20 and 40 vs 80? My eyes can't tell). So how does one determine whether or not something is reading correctly other than having trust in some other test? Especially when all the tests are giving a reading of something greater than 0 (unlike OP's case). 

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24 minutes ago, StephenP2003 said:

I always hear about the liquid being inaccurate even when you shake the heck out of it, but the problem is neither test (strips or liquid) is super exact (honestly, 10 vs 20 and 40 vs 80? My eyes can't tell). So how does one determine whether or not something is reading correctly other than having trust in some other test? Especially when all the tests are giving a reading of something greater than 0 (unlike OP's case). 

Agreed. I did a whole post about this a little while ago; there's so much variation in determining what color those strips are. Interestingly, the Tatra strips actually have an app that will automatically read the color, but... how accurate is that, with variations Iighting? It's a constant struggle.

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I suspect that, even though I said I dosed properly, I'm not doing so (see below). But I'm not going to analyze further with these ferts. I  just bought some Easy Green and will use it.

The thing is (and I'm sort of answering my own question), liquid tests are titrations. Assuming the test kit reagents are correct and the testing procedure followed properly , it's not possible for them to be wrong or inaccurate. 

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2 hours ago, StephenP2003 said:

I always hear about the liquid being inaccurate even when you shake the heck out of it, but the problem is neither test (strips or liquid) is super exact (honestly, 10 vs 20 and 40 vs 80? My eyes can't tell). So how does one determine whether or not something is reading correctly other than having trust in some other test? Especially when all the tests are giving a reading of something greater than 0 (unlike OP's case). 

You make up or buy a reference or calibration solution https://www.amazon.com/HORIBA-3200053536-Nitrate-Standard-Solution/dp/B00DD5ATB4

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I don't believe it's an issue with the test kits rather the seachem fertilizer is weak sauce. 

Some quick math with some rounding. 

40 gallons is approximately 150,000 ml.  For simple understanding we can multiply by 6.66 to get 266 gallons or 1million ml. So following the directions we dose 2.5ml per 40 gallons. 6.66 doses gets us 16.66 ml going into 1,000,000 ml of water. So we have 16.66 ppm of seachem fertilizer in the tank. But how much of that fertilizer is actually nitrate. According to their website not very much. 

Ingredients

Amounts per 1 g

Total Nitrogen (N)1.5%

Soluble Potash (K2O)2%

Derived from: potassium nitrate, urea

1.5% of our 16.66 ml is nitrogen. 1.5% of 16.66 is about 0.25. So following their dose it would be basically impossible to see that change on a nitrate test. But it gets even worse. Only part of the nitrogen in seachem nitrogen is nitrate. The other source is Urea which is ammonium. Ammonia tests are much more sensitive but I still suspect that less than 0.25 ppm of ammonia is still challenging to notice on a liquid test kit. 

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I’ve always found the API nitrate test to be high, especially when compared to other tests. I use the Salifert nitrate test as my reference for accuracy. It always seems to land in the middle of the 3 nitrate test kits that I use. 
 

I’m sure that it’s just me, but I don’t trust test strips at all. 

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51 minutes ago, L.W. Wetarm said:

I’ve always found the API nitrate test to be high, especially when compared to other tests. I use the Salifert nitrate test as my reference for accuracy. It always seems to land in the middle of the 3 nitrate test kits that I use. 
 

I’m sure that it’s just me, but I don’t trust test strips at all. 

didn'tt know salifert did freshwater 

 

15 hours ago, ChrisD said:

A few hours after properly dosing ( based on directions) my planted tanks with Seachem Flourish, Searchem Nitrogen, (and Flourish Excel though it should  be irrelevant), my API test kit indicates 0 ppm of nitrates. Should this be the case? If not, perhaps could it be a problem with the test kit?

 

yeah i noticed the same thing

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You should go on my profile and check out my post about seachem flourish excel cause I go more in depth about it. But I SWEAR flourish excel lowers nitrates. idk why or how. but im 100% it does for me. like I said i got detailed observations about it in my other post that I would recommend checking out. Maybe that the answer to ur question and the reasoning for the low nitrate levels even after adding ferts. I can't prove it tho, lol.

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I know that when I was trying to cycle my first tank a couple years ago, I kept testing and testing and testing and waiting for nitrates to appear with the API test kit...nothing.  After several weeks, I finally took it to my LFS, and they tested for me.  Nitrates were there all right--I learned that you have to shake and shake and even bang the bottle on the counter and shake some more to get the solution to work. 

It seems to form crystals inside the bottle and then there's not enough of whatever reacts with the nitrate suspended in the bottle solution to work unless you break up the crystals.  I have a hard time reading the colors on the chart as well--20--40--80? --depends on the light, but if you think nitrates should be there, and you're not seeing them, give banging and shaking a try 🙂  

Another option would be Tetra test strips--Cory did a video comparing them to the API kit and they come out quite accurate, easier to use, and cheaper (esp. if you cut them in half lengthwise).  They match for me when I do both, and I find the colors SLIGHTLY easier to read than API.  You could see what they say about nitrate and get an idea if it's an issue with using the API test or if the water is actually nitrate free.

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  • 1 month later...
On 12/19/2020 at 11:24 PM, StephenP2003 said:

honestly, 10 vs 20 and 40 vs 80? My eyes can't tell

I am so relieved! I thought it was me. However, I cannot read the nitrate test on the upper end, and I'm afraid I've grown complacent about the levels. My nitrate always seems a bit high (how high? :classic_unsure: dunno.) I thought pothos and other plants were supposed to help with that, so I'm a bit confused.

I guess I need to knock back the feeding a bit and stop dosing with Easy Green(?). I also have some plants that are shedding leaves, but I've ordered some snails off eBay  (Good money for "pest" snails — it's a sad day 🤣), so hopefully they will help with extra food and plant waste. Plus I remember Rachel O'Leary saying pest snails are excellent barometers for a tank's balance. Too many snails means too much food in the tank, so I'm looking forward to that, as well.

What else can I do? I really don't want to stop dosing Easy Green, as my java ferns are making babies and are looking a little unhappy. Would welcome suggestions, as I am always a little shaky on the chemistry.

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13 minutes ago, Celly Rasbora said:

I am so relieved! I thought it was me. However, I cannot read the nitrate test on the upper end, and I'm afraid I've grown complacent about the levels. My nitrate always seems a bit high (how high? :classic_unsure: dunno.) I thought pothos and other plants were supposed to help with that, so I'm a bit confused.

I guess I need to knock back the feeding a bit and stop dosing with Easy Green(?). I also have some plants that are shedding leaves, but I've ordered some snails off eBay  (Good money for "pest" snails — it's a sad day 🤣), so hopefully they will help with extra food and plant waste. Plus I remember Rachel O'Leary saying pest snails are excellent barometers for a tank's balance. Too many snails means too much food in the tank, so I'm looking forward to that, as well.

What else can I do? I really don't want to stop dosing Easy Green, as my java ferns are making babies and are looking a little unhappy. Would welcome suggestions, as I am always a little shaky on the chemistry.

I have a couple tanks that do a great job making their own nitrates, so I have to dose something lower in nitrogen. I keep the nitrates orange, and that's the extent of my worrying over it. 

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Hi All,

I have done planted tanks for over 12 years now and have used the API Nitrate Test Kit(s) for all those years.  I have probably done well over 400 tests in total.  Whenever I get a new test kit I test it against a calibrated solution using the Rex Grigg method of making up the solutions.

 

Quote

Testing Your Nitrate Test Kit

  • Take 1000ml of water. Dissolve 6.5 grams of KNO3 in it.
  • Take 1 gallon of water. Each ml of the above solution will add 1 ppm of NO3.
  • Add 5 ml, test. Your test kit should show 5 ppm.
  • Add 5 more ml, test. Your test kit should show 10 ppm
  • Repeat through the range of your test kit.

I have found the API Nitrate Test Kit to be very, very accurate.  -Roy

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