Added 1/2 tsp KNO3, ended up with 80ppm NO3 ? - The Planted Tank Forum
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post #1 of 17 (permalink) Old 10-22-2005, 04:21 PM Thread Starter
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Added 1/2 tsp KNO3, ended up with 80ppm NO3 ?

I'm really confused. 55 US Gallon aquarium

I did a 50% water change. Tested my nitrates. 5ppm.
Added, (as per Wolfen's sticky):

0.5 tsp KNO3
0.125 tsp KH2PO4
10ml Trace (1 tbsp mixed 250ml water)

Tested for nitrates and it's anywhere from 40-80ppm, maybe more.

No mistake, I double tested.

Now I should be adding this much 3x a week? That doesn't seem right to me.

According to the fertilator at APC this should have added 7.6ppm NO3.

What went wrong?
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post #2 of 17 (permalink) Old 10-22-2005, 04:28 PM
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Nothing went wrong unless you did not know a teaspoon from a measuring cup.

I always figure my 55 gallon tank holds about 48 gallons of water. teaspoon of KNO3 will raise 48 gallons of water to around 9.4 ppm of NO3.

These are physical constants.

Your test kit is bad or you need to RTFM.
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post #3 of 17 (permalink) Old 10-22-2005, 04:35 PM Thread Starter
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Any mature person have any suggestions to offer?
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post #4 of 17 (permalink) Old 10-22-2005, 05:14 PM
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well, he was right... not sure what was "immature" about it.

Your testkit is bad. KNO3 ppm increases are exactly what the calculators say. Can't possibly increase by more or less. Unless maybe if it is old, but then it would merely weaken instead.

what does RTFM mean anyway?

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post #5 of 17 (permalink) Old 10-22-2005, 05:17 PM Thread Starter
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(His attitude is immature. Not something I'd expect from an adult.)

RTFM means Read The [censored][censored][censored][censored]ing Manual.

I just had a thought. The dry fertilizer KNO3 I got could be bad...
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post #6 of 17 (permalink) Old 10-22-2005, 05:23 PM
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I'd wait a couple of hours then retest. If it's still that high, 50% wc again. Don't add any KNO3, leave it overnight, then test again, see what happens.
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post #7 of 17 (permalink) Old 10-22-2005, 05:25 PM
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Don't put to much weight on those $10 test kit's, they lie!

Use the plant's, fish and algae as a test kit, they do not lie!

How much $$$ do you have invested in you're tank?.
How much $$$ do you have invested in you're test kit?.

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post #8 of 17 (permalink) Old 10-22-2005, 05:35 PM Thread Starter
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Quote:
Originally Posted by Tino
I'd wait a couple of hours then retest. If it's still that high, 50% wc again. Don't add any KNO3, leave it overnight, then test again, see what happens.
Thanks. I'll do that and post results here tomorrow. =)

Quote:
Originally Posted by WfxXx
Don't put to much weight on those $10 test kit's, they lie!

Use the plant's, fish and algae as a test kit, they do not lie!

How much $$$ do you have invested in you're tank?.
How much $$$ do you have invested in you're test kit?.

That's a good point... but still.. it's quite unnerving to go against what I assume should be accurate!


Anybody feel like letting me send them a sample of my KNO3 and running some tests on it?
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post #9 of 17 (permalink) Old 10-22-2005, 06:09 PM
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If your KNO3 is bad it would give low readings. But it's a pretty inert substance and really doesn't go "bad". It's not milk or shrimp, or an ex-wife. I have KNO3 that is almost 5 years old and while it is slightly discolored it still works just like it did the day it was new.

People having problems with Nitrate test kits is very common. They don't shake the regent bottles long enough or at all, they don't shake the sample long enough or at all. That's why the suggestion to RTFM.

When most nitrate test kits go bad they give artificially high readings.

There are very few variables here. Some people don't or didn't know there was a difference between tablespoons and teaspoons. Some people don't or didn't know that when using measuring spoons you always use a level measurement. Some people don't or didn't know that the spoons you eat with are not even close to being tablespoon or teaspoon measurements.

So we can break it down to just a couple of things.

You made a mistake in the amount of KNO3 you added to the tank.

Or......

You made a mistake in the testing procedure.

Or......

Your test kit is bad.


It's your pick.

You stated you assume your test kit to be accurate. You know what happens when you assume something?

To test the test kit take 1 gallon of water. Add teaspoon or 1.4 grams of KNO3 to it.

Take cup of that water and mix it with 2 cups of water. Take a sample and test it. It should test out to be 20 ppm with a good test kit.
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post #10 of 17 (permalink) Old 10-22-2005, 06:10 PM Thread Starter
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Just tested my tap water and it's approx 10ppm.
Plus the 5ppm in the tank, and 10ppm added from KNO3, and given human and test kit inaccuracy, I feel pretty comfortable about it.
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post #11 of 17 (permalink) Old 10-22-2005, 06:13 PM Thread Starter
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Quote:
Originally Posted by Rex Grigg
If your KNO3 is bad...

<Snip>

...It's your pick.
Well, I apologize for taking your comments so sensitively. That's interesting to know that KNO3 doesn't go bad. I don't know how they go about mixing up a batch of it, but is it not possible that they accidentally added too much NO3?

Anyway, like I said, the tap water and human and test kit inaccuracy probably has a lot to do with it...
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post #12 of 17 (permalink) Old 10-22-2005, 06:14 PM
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I still think your test kit is bad. And if your error rate is a factor of 5X then that's a problem.

10ppm + 5ppm = 15 ppm. You tested 40-80 ppm. That's an error rate of 3X to 5X.
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post #13 of 17 (permalink) Old 10-22-2005, 06:20 PM
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I just checked your cities Water Quality report. If you are on city water then there is NO way your water has 10 ppm. At most it appears it would run just under 1 ppm.

Inconsistent readings is a test kit going bad.
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post #14 of 17 (permalink) Old 10-22-2005, 07:11 PM
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Quote:
Originally Posted by Rex Grigg
I just checked your cities Water Quality report. If you are on city water then there is NO way your water has 10 ppm. At most it appears it would run just under 1 ppm.

Inconsistent readings is a test kit going bad.
According to the materials sent by my water company, Bridgeport Hydraulic, 10PPM is allowed by law in Connecticut. Many different test kits for me have shown around a 3-5 range for water out of the tap.

Pseud is supplied water by a different company than I am, but I believe he is just "upstream" from me. So there may be similarities in the water. I know mine test's out a lot like Marcel's. And he's not far from Pseud.

That said, 5ppm is still a long way off from answering this problem...

Steve - 33g reef and a 180g planted in need of a re-scape.
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post #15 of 17 (permalink) Old 10-24-2005, 06:46 PM
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I suspect the initial tank NO3 reading at 5ppm was too low. As Rex pointed out, one can often get false low readings if the reagent was not shaken long/hard enough. I was a victim of that myself before, I kept adding KNO3 thinking my reading was still low until one day, boom, I got 40-80ppm reading.

Also you can't simply add up tank NO3(5ppm) and tap NO3(10ppm) after you change water. For example, if you changed 50% water, then it should be 7.5ppm for the whole tank, not 15ppm.

Quote:
Originally Posted by Pseud
I don't know how they go about mixing up a batch of it, but is it not possible that they accidentally added too much NO3?
It does not work that way. You can't just get the NO3 part without the K part. NO3- can not exist by itself without something else, that something else happens to be K+ in this case, well, minus small amount of impurities.


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