# [Wet Thumb Forum]-KNO3/Testing Question



## Vinlo (Jul 27, 2004)

In recent weeks I have been trying to get a dosing schedule down. I have encounter several problems in the way of Nitrate test kits. I finally have one that works, a Seachem one.. tested with the 10ppm stock solution and everything appears fine. Here is my problem on my 30g tank..

I tested my tank, it read 0ppm..
I added 1/4tsp (~5ppm) of KNO3 (disolved in a small bowl and then added to the tank)
Tested again a day later.. still 0ppm
Added more KNO3..
Tested again.. still zero
Did a water change and added 1/2tsp of KNO3 (~11ppm)
Tested tank 2 hours later.. still zero?!?

I am using KNO3 that I bought at a hydroponics store. It has a guaranteed analysis of 12% Nitrogen (N) and 44% Soluable Potash (K20). What is the other 44%? Now could this KNO3 be my problem? I am really at a loss here so any help is grealy appreciated!

_____________________________
30g, 2wpg (NO Fluorescent), 90% Flourite, DIY CO2, HOB


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## Vinlo (Jul 27, 2004)

In recent weeks I have been trying to get a dosing schedule down. I have encounter several problems in the way of Nitrate test kits. I finally have one that works, a Seachem one.. tested with the 10ppm stock solution and everything appears fine. Here is my problem on my 30g tank..

I tested my tank, it read 0ppm..
I added 1/4tsp (~5ppm) of KNO3 (disolved in a small bowl and then added to the tank)
Tested again a day later.. still 0ppm
Added more KNO3..
Tested again.. still zero
Did a water change and added 1/2tsp of KNO3 (~11ppm)
Tested tank 2 hours later.. still zero?!?

I am using KNO3 that I bought at a hydroponics store. It has a guaranteed analysis of 12% Nitrogen (N) and 44% Soluable Potash (K20). What is the other 44%? Now could this KNO3 be my problem? I am really at a loss here so any help is grealy appreciated!

_____________________________
30g, 2wpg (NO Fluorescent), 90% Flourite, DIY CO2, HOB


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## Roger Miller (Jun 19, 2004)

Pure KNO3 would be 14% N, 47% K2O and 40% O2. Your KNO3 is not very pure. Most of the remaining 44% is oxygen and some no doubt is water. Technical and agricultural grade chemicals always contain impurities.

I can't say exactly what the impurities (other than water) might be. One possible explanation is that the stuff is about 87% KNO3, about 4% K from some other source and about 9% other compounds -- including water -- that contain neither K nor N.

If careful reading of the label doesn't tell you what the impurities are then you might be able to find a more detailed analysis from the MSDS (Materials Safety Data Sheet) for the product.

I can't help much with reasons why the kit doesn't seem to be working. I suppose it's possible that whatever is in the product you bought is not KNO3. That would be odd.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Vinlo (Jul 27, 2004)

Thanks Roger, I am going to call the place that I got it from today and try to get an MSDS sheet or see if they can provide any answers. If they cannot I just may order some from gregwatson.com unless Robert sells it?

I am guessing it is the KNO3 since the test kit registers the proper value compared to the 10ppm stock solution.

After reading a post on APD I was wondering if anyone else has had problems getting a reading of NO3 with a seachem test kit dosing KNO3?

Thanks for the help.

_____________________________
30g, 2wpg (NO Fluorescent), 90% Flourite, DIY CO2, HOB

[This message was edited by Vinlo on Sat January 17 2004 at 07:21 AM.]


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## Planted Engineer (Jan 15, 2004)

Hi,

I found a 12-0-43 fertilizer and the title says: "multikot - slow release fertilizer". The product analysis says 12% N, 43% K2O and 0.2% chlorine. The product description says that it is postassium nitrate and that it is a 'slow releasing' one because it's grains are covered with a non soluble polimer.

My first question would be... - Could it be that although it's close to the 14-47 of the pure KNO3 - this is not a KNO3 at all???? Could it be that this is mixture but not a compound? If I pour this stuff into the water - Do I get KNO3?? 

My second question is regarding the added ingredients... Chlorine is a problem but is 0.2% OK for the fish? Would it make sense to mix the stuff with water and then wait for the chlorine to evaporate? What about the polymer - could it be hazardous to the fish?

PE.


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## Roger Miller (Jun 19, 2004)

> quote:
> 
> My first question would be... - Could it be that although it's close to the 14-47 of the pure KNO3 - this is not a KNO3 at all???? Could it be that this is mixture but not a compound? If I pour this stuff into the water - Do I get KNO3??


The only way it isn't KNO3 is if the label is an outright lie. I think that is highly unlikely. If you dissolve it in water you will get K+ and NO3-. Probably to dissolve it in water you will want to crush the polymer-cloated beads.



> quote:
> 
> My second question is regarding the added ingredients... Chlorine is a problem but is 0.2% OK for the fish? Would it make sense to mix the stuff with water and then wait for the chlorine to evaporate? What about the polymer - could it be hazardous to the fish?


The impurities probably wouldn't be added, they are just part of the original manufacturing process that has not been purified out of the product. The chlorine is almost certainly present as chloride, which is benign. Certainly 0.2% would be negligible. There may be more information available on the MSDS.

Polymer coatings have been used on fertilizers for a while now -- on Osmocote, for instance. There is some experience using coated beads in aquariums and I have never heard of them causing problems for fish or inverts.

The contents of the beads dissolves slowly through the polymer coating, leaving an empty shell. A collection of little spherical beads in the tank isn't usually real unattractive, but it may be distracting.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Vinlo (Jul 27, 2004)

I completely dissolve the beads before I add it to the tank. I could not get a hold of the company which I bought the KNO3 from for the MSDS sheet. I did however buy another Redsea Nitrate test kit, it gave me a reading of ~10-15ppm.. so I guess that is about what should be in the tank. 

I am going to mix a stock solution and test that. It reads 0ppm of Nitrate in my tap water (this checks out with local water analysis that I looked up on the net. Slowly but surely I will track down what is happening with this crazy problem.

_____________________________
30g, 2wpg (NO Fluorescent), 90% Flourite, DIY CO2, HOB


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## Planted Engineer (Jan 15, 2004)

OMG,

got 20 ppm instead of the expected 5 ppm NO3...










OK - here's what I have done. I bought a somewhat different product from the above - and it says 13% N ("in the form of NO3"...) and 46% K2O. It looks like the same product - the grains are somewhat big probably coated etc.

Now I took this NO3 and dilluted 6 tsp in 1000 mL and shaked vigorously... ;-)

I then added 2 tsp to my 10 Gallon experiment Aquarium...

Chuck Gadd calculator estiamted 5 ppm. I got 20!!!

All fish are OK.

Now please review my explanation for this... - What I got from the grains was only the N whose molecular weight is 14. Inside the water it added 3O with 16 molecular weight so - 14 + 3 * 16 is ~4 times KNO3 than I expected. Therefore I got 20 ppm instead of 5 ppm.

Does my explanation make sense?

PE.


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## Roger Miller (Jun 19, 2004)

Your explanation would work if Chuck's calculator gave results for the concentration of nitrogen. It doesn't. Chuck's calculator gives results for nitrate, so you need a different explanation.

Here's one possible alternative. Is it possible that you used 6 tablespoons of KNO3 instead of 6 teaspoons when you made up the stock solution? Combine that with the fact that a 10 gallon tank doesn't usually contain 10 gallons of water and the 20 ppm is explained:

6 tablespoons in 1000 mls gives a solution that when dosed to 8 gallons of water will produce a concentration of about 2 ppm/ml. Two tablespoons dosed to the tank then would be 10 mls, so the resulting nitrate concentration would be 20 ppm.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## Planted Engineer (Jan 15, 2004)

Hi,

It was a tea spoon - the one you typically add sugar with and not the one you eat your soap with...









Let me try again to explain my "theory" - please don't shoot me if I am wrong cause this is the first time I look at molecular weight after 26 years...









I was holding in my hand something that had N in a concentration of 13%. I thought I was holding NO3 in my hand in a concentration of 69%. I used Chuck's calculator and aimed for 5 ppm. But when I poured the thing into the water those 6 teaspoons became ~24 teaspoons because for each N that I was holding in my hand 3 O atoms were added... I might be talking nonsense here if you come and say that it was impossible for me to hold N in my hand... It already includes the O3 - This is something that I just don't have the knowledge.

Thanks for your support (I have been silently reading many of your posts and I am very impressed)

Aviel.


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## Rex Grigg (Jan 22, 2004)

Ok, first problem is it sounds like you were NOT using measuring spoons but common flatware. There is no standard on flatware. I checked the math on Chuck's calculator and if you add 6 teaspoons of KNO3 to 1000 ml of water each ml that you dose into a 10 gallon tank will give you 0.55 ppm. You said you dosed 2 teaspoons of this mixture which is around ~9 ml. Now my question is do you know if your test kit is accurate?










American by birth, Marine by the grace of God! This post spell checked with IESpell available at http://www.iespell.com

See my Profile for tank details.

See my planted tank FAQ at http://members.dsl-only.net/~rex/


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## Roger Miller (Jun 19, 2004)

Aviel,

Your calculations aren't far off, but they don't solve your problem. Chuck Gadd's calculator doesn't use the 13% N from your analysis. Results from Chuck's calculations are based on KNO3 being 61.2% NO3. Let me go through the whole calculation:

From Chuck's page,

KNO3 is 61.2% NO3
KNO3 weighs 5.6 grams per teaspoon

6 teaspoons of KNO3 contains 6*5.6*0.612=20.6 grams of NO3

You mix this with 1000 ml of water, then dose with 2 teaspoons, or about 10 ml, so you add to the tank 20.6*10/1000=0.206 grams of NO3, or 206 mg of NO3.

You add that 216 mg of NO3 to a 10 gallon (38 liter) tank, so the resulting concentration is 206/38 = 5.4 mg/l of NO3.

As you surmised, there is about 4 (actually 4.4) milligrams of NO3 for each milligram of N. The 5.4 mg/l of NO3 translates to 5.4/4.4 mg/l of N, or 1.2 mg/l of N.

The product you used is 13% N, so it isn't quite pure KNO3. !3% N translates to 13*4.4 or 57% NO3. If you used 57% in the calculations above instead of 61.2% then the end result would be a tad lower -- just about 5 ppm NO3.

So the problem really needs to be in something you did or with your test kit. As Rex pointed out, if you used flatware for measurement then the measurements are off. The other possibility is that the test kit is wrong by a factor of 4.

I don't know about your flatware, but the normal spoons in my flatware hold quite a bit more than a teaspoon. A rounded "teaspoon" would be about the same as a real tablespoon. A rounded sugar spoon would be even bigger. The sugar spoon is practically a ladel. I think it's a sugar spoon for modern America.

Roger Miller

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_"The indispensible first step to getting the things you want out of life is this: Decide what you want" -- Ben Stein_


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## JLudwig (Feb 16, 2004)

> quote:
> 
> I think it's a sugar spoon for modern America.


Good planted tank advice and poignant social commentary, what more could you want from a post?









Still wondering where all that iron goes,
Jeff


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