# API test kit question



## underwatergirl (Nov 26, 2012)

Sounds silly, but since it's not mentioned in the directions about holding it in front of the chart, exactly how far away should you hold the vile? Even in a well lit area, if it's held directly up against the card, my nitrates look like 40ppm or more. BUT if it's moved away even 1/2", the reading looks like 10ppm. Maybe I've been reading it incorrectly. I don't think my fish would spawn all the time if nitrates were consistently 40ppm or higher. Thanks!


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## Deeda (Oct 12, 2012)

My instructions state to "hold the tube against the white area next to the color chart" and to view in a well lit area.

Try looking down through the tube (without the cap on) against the white background as it may be more helpful to choose the color match.


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## Wilson33 (Feb 19, 2008)

Reading the nitrate test is difficult for me, too. Deeda's advice is very sound.

What I did was change about 25% of the water for a few days until the nitrate test obviously read less than 20 ppm. I now just change 25% of the water every 3 days or so, and everything is fine. You are probably fine as is, I am pretty sure that I was.


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## triscuit (May 6, 2005)

Looking down through the tube will give a different reading; the card is color coded specifically for the tube to be read against the card, and through the side. Colorimetric tests are subjective by nature, but until you reach a color closer to 10 ppm, it's a bit pedantic to worry if you are at 30 or 40 ppm.


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## underwatergirl (Nov 26, 2012)

Well if that's the case, nothing that I'm doing is helping much. 2 days of 50% change, then a 75% change. It was slightly(?) better after that change.


triscuit said:


> Looking down through the tube will give a different reading; the card is color coded specifically for the tube to be read against the card, and through the side. Colorimetric tests are subjective by nature, but until you reach a color closer to 10 ppm, it's a bit pedantic to worry if you are at 30 or 40 ppm.


What do you mean "through the side"?


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## triscuit (May 6, 2005)

Stand the tube up on your table, then hold the card up behind the tube so that when you look at the color, you've got a white background behind the tube right next to the color chart. And yes, fish will breed in poor water quality, and its not unusual for long term tank setups to have high nitrates.

Now the interesting part is why you don't see incremental drops in your nitrate concentration. First, the test results are not linear, and the test accuracy is best a low concentrations. The next problem is that every time you do a water change, more nitrates become dissolved from any solids still in your tank. It can take a few weeks of large water changes to get consistent low nitrate readings.

One way to help determine the accuracy of your test results is to do a series of dilutions. Start with all tap water, then try 25% tank water, then a 50/50 mix.


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## underwatergirl (Nov 26, 2012)

triscuit said:


> Stand the tube up on your table, then hold the card up behind the tube so that when you look at the color, you've got a white background behind the tube right next to the color chart. And yes, fish will breed in poor water quality, and its not unusual for long term tank setups to have high nitrates.


Ok, I've been doing it correctly, just confused me when you said from the side  . Hmmm, about the breeding...everything I've been told on the forum before is that my water parameters must be really good for them to readily breed.


triscuit said:


> One way to help determine the accuracy of your test results is to do a series of dilutions. Start with all tap water, then try 25% tank water, then a 50/50 mix.


Pictured left to right: 100% tap water, 50/50, 100% tank. What are your thoughts? I appreciate the advice.


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## triscuit (May 6, 2005)

Very cool pic! Thanks for posting! 
But now we see that your tap water has weirdly high nitrate, and so I'm wondering about your test kit. Assuming you are using the correct amounts of reagents, it's unusual to see that level of contamination. Otherwise, your tank water has about 30ppm, so a few more water changes and substrate vacuuming should bring it down. But if you are starting with ~10ppm in the tap, it's going to be hard to get the tank below 20ppm.


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## Wilson33 (Feb 19, 2008)

One thing that can throw off this test is if the plastic bottle containing reagent #2 has not been shaken vigorously for at least 30 seconds before adding the drops. If the bottle has not been shaken before each and every test, then the kit is no longer accurate. I was simply mentioning this because of the level of nitrate in your plain tap water. I remember reading about this issue in an older thread. The member got a new test kit, and the nitrate levels were completely different from the old kit.


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## ozman (Sep 7, 2012)

also in the pic above you have your test tubes filled beyond the mark on the side. :-? i have concerns that you are not using your test kit as per the manufactures instructions.
as said by wilson33 have you been shaking the bottles vigorously before use? inmo it would only take once that you did not use correctly to throw out your readings, and basically your kit if thats the case needs to be replaced.


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## timbo6684 (Aug 29, 2010)

ozman said:


> also in the pic above you have your test tubes filled beyond the mark on the side. :-? i have concerns that you are not using your test kit as per the manufactures instructions.
> as said by wilson33 have you been shaking the bottles vigorously before use? inmo it would only take once that you did not use correctly to throw out your readings, and basically your kit if thats the case needs to be replaced.


Once you've added the twenty drops in total it's going to raise the volume of liquid passed the line.


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## Deeda (Oct 12, 2012)

ozman, don't forget that adding 10 drops from each reagent bottle is increasing the test sample.

I also second Wilson33's comment about following the test instructions exactly, especially regarding shaking reagent #2 for 30 seconds prior to dispensing it.

One other thing that may be overlooked is the container that your using to take the water sample from your aquarium. I prefer to use a clean glass container such as a measuring cup or small Pyrex bowl, rather than plastic to avoid any problems with the plastic having absorbed any contamination.

The pic you posted of the different test results was helpful and I agree that something is off. Hopefully it isn't your tap water but is your sample and testing procedure that is skewed.


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## underwatergirl (Nov 26, 2012)

triscuit said:


> Very cool pic! Thanks for posting!
> But now we see that your tap water has weirdly high nitrate, and so I'm wondering about your test kit. Assuming you are using the correct amounts of reagents, it's unusual to see that level of contamination. Otherwise, your tank water has about 30ppm, so a few more water changes and substrate vacuuming should bring it down. But if you are starting with ~10ppm in the tap, it's going to be hard to get the tank below 20ppm.


Thanks Triscuit. I'll continue with water changes and vacuuming, hoping this brings it down. Things I use in my tank/filter: Prime, Purigen, and Poly Filter (plus a few plants). I've used nitrazorb in the past but with having to recharge every 5 days, I decided to try Purigen and Poly filter--coincidence: found out it's made in my home town!
Prior to this, I had been doing 30-40% weekly water changes, but I wasn't doing aggressive vacuuming since it is a "newer" set up (under 6 months) and had read you should just siphon off the top to let biological take hold. Maybe they were only referring to "new" (6-12 months) because we were discussing diatoms.  
BTW, in a new setup, when SHOULD you start a more thorough vacuuming? Couldn't find answers on forum.


timbo6684 said:


> ozman said:
> 
> 
> > also in the pic above you have your test tubes filled beyond the mark on the side. :-? i have concerns that you are not using your test kit as per the manufactures instructions.
> ...


+1 timbo6684. The bottom of the meniscus hits the line before adding the reagents. I'm anal with following the directions (not just with these test kits :lol: )
Thanks for everyone's help!


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## triscuit (May 6, 2005)

It's important to note that colorimetric tests rarely fail by measuring too much analyte. Most failures, especially those involving poor mixing, result in under detection.

So, Underwatergirl, I'd suggest bringing in a tap water sample to be tested in a local store, but unless you get a skilled and knowledgeable employee, your results are going to be more accurate. Are you on city water, or do you have a well? Is this tap water also your drinking water?


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## underwatergirl (Nov 26, 2012)

triscuit said:


> It's important to note that colorimetric tests rarely fail by measuring too much analyte. Most failures, especially those involving poor mixing, result in under detection.
> 
> So, Underwatergirl, I'd suggest bringing in a tap water sample to be tested in a local store, but unless you get a skilled and knowledgeable employee, your results are going to be more accurate. Are you on city water, or do you have a well? Is this tap water also your drinking water?


I'm on city water, and we don't drink it. We use filtered water from the fridge.


Deeda said:


> One other thing that may be overlooked is the container that your using to take the water sample from your aquarium. I prefer to use a clean glass container such as a measuring cup or small Pyrex bowl, rather than plastic to avoid any problems with the plastic having absorbed any contamination.
> 
> The pic you posted of the different test results was helpful and I agree that something is off. Hopefully it isn't your tap water but is your sample and testing procedure that is skewed.


I've never used a separate container...is that important? I just dip the vials in the tank.


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## ozman (Sep 7, 2012)

ozman said:


> also in the pic above you have your test tubes filled beyond the mark on the side. :-? i have concerns that you are not using your test kit as per the manufactures instructions.
> as said by wilson33 have you been shaking the bottles vigorously before use? inmo it would only take once that you did not use correctly to throw out your readings, and basically your kit if thats the case needs to be replaced.


i apologise re the marks on the vial  i was going by using the sera kits that when i used them last did not rise way above the line like that.

but still i stand by my remark about using your test kits correctly.


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## triscuit (May 6, 2005)

underwatergirl said:


> I've never used a separate container...is that important? I just dip the vials in the tank.


That's what I do... I just make sure they are very clean, and then I fill them several times in the tank before taking my sample.


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## underwatergirl (Nov 26, 2012)

IDK, maybe our tap water goes through different cycles, this happened to me before. I just tested the tap again and got the same results. I'll take a sample to lfs of tap and both tanks, along with my test kit and let them do several tests--with mine and theirs.


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## Wilson33 (Feb 19, 2008)

It is not unusual for cities to tinker with their water. I hope that you can find some kind of answer soon.


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