EI - 40ppm nitrate in tap water

ilaizm

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Feb 23, 2009
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In my tap water I have a nitrate level of 40ppm. Does that mean I should skip KNO3 in my dosing regime?
 

Tom Barr

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Yes, assuming it's really 40ppm and stays around that amount.
Use K2SO4 at similar amounts of KNO3(maybe a tad less).

Regards,
Tom Barr
 

ilaizm

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Feb 23, 2009
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Ok thanks!

I bought two different nitrate test kits to make sure its correct and it came that high with both of them. So yes it has 40ppm.
 

Tom Barr

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No, that is NOT the method to test or have any such confidence about the test results.

You must make a calibration solution, generally 2-3 points, say 5ppm and 20ppm, or 1,10, 50ppm etc.

Then..........you have claibrated the test kit and know what the NO3 is, or.........is not.

I've seen two kits both measure 40ppm and the water was 0 ppm.
Maybe it is, maybe it is not, call your water district and ask them also.

See how to make a calibration solution for NO3 from Left C's post.

Regards,
Tom Barr
 

ilaizm

Junior Poster
Feb 23, 2009
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Oh I see!

So after preparing the reference solutions what do you do exactly? Do you use the test kit on the reference solution to see how accurate the test kit is and then run an actual test with tap water?
 

jonny_ftm

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Mar 5, 2009
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You can make a test with calibrated solution and the tap water using similar containers. Then compair at direct daylight the results between two containers.

Just for your info, tetra tests and JBL ones are really bad. I tried many, even Sera tests. The best test that I could verify calibration was Salifert NO3 test, sensitive up to 0.2 ppm NO3, and with a scale of 0-0.2-0.5-1-2.5-5-10-25-50-100 ppm

http://www.marinedepot.com/ps_AquariumPage~PageAlias~test_kits_salifert_nitrate_information.html

I have RedSea test that I didn't verify accuracy yet

Finally, if your tap is really 40ppm, I wonder if using distilled or RO isn't a good idea
 

priv_sim

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Nov 29, 2006
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Why are those tests bad(JBL, tera)? I think if u are using reference solution any test should be fine, unless you dont follow the instructions.
 

jonny_ftm

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Mar 5, 2009
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priv_sim;36617 said:
Why are those tests bad(JBL, tera)? I think if u are using reference solution any test should be fine, unless you dont follow the instructions.

Give them a try with reference solutions and you'll see how they fool you
JBL detects 1/2 to 1/4 the actual value
Tetra often detects 20ppm even at 0 ppm and is not sensitive to low values
Sera starts at 10ppm only then big steps
 

Gerryd

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Sep 23, 2007
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ilaizm,

Yes, after preparing a KNOWN solution, you use the reference solution and test it. It SHOULD match the value of the reference solution.

This is to verify the ACCURACY of the test method/kit.

Once the accuracy is verified you can then test any other sample.

Many of the test kits sold are not that accurate. many folks get burned by false readings.

Hope this helps.
 

Tom Barr

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The cheapo test kits may.....or may not be accurate, only by verifying that they are, can we have any confidence and make decisions based on those readings.

So we calibrate them, then check the test kit against the known standards.

This is true for 10,000$ lab equipment or the 8$ test kit you buy at the local fish shop. The same calibration needs done and once every 1-2 months there after.

JBL, Sera, Lamotte etc, all are not going to be accurate, some might be etc, but you should always have a reference to compare to make sure. It's not their fault, it's just the way testing is done.

You check and confirm if you want to be sure or plan on using the info to make dosing changes or believe that there's a big difference between adding 30ppm or 40ppm of NO3.


regards,
Tom Barr
 

VaughnH

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Jan 24, 2005
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For most of what we use a test kit for, you don't need the accuracy of a digital scale. You can use ordinary kitchen equipment, by following this: Calibrating Test Kits - for non-Chemists This isn't good enough to satisfy someone who wants to know "exactly" how much nitrate is in the water, but most of us just want to know that if the test kit says we have 40 ppm, it isn't really 1 ppm or 10 ppm.