# Test kit accuracy



## sc204 (Nov 17, 2007)

Even though people have said you can dose PPS pro without measuring levels I am one who likes to know where everything is at so the system can be fine tuned. I have a large tank approx 500 gallons with 900 gallons total volume including filter and sumps. I am dosing PPS pro at 30 cc of each per day at Edwards suggestion based on the amount of plants that I have. So I am already much less than the 1cc per 10 gallon rule. Also using CO2 and MH lighting. I used to use Tetra test kits and feel that they seem to be fairly good. I use Lamotte for alkalinity and hardness for more accurate results with my pretty soft water. Most of my Tetra tests had run out and are not carried locally. I bought a couple of Red Sea test kits including Nitrate. The color chart for the Red Sea kit seemed to show a nice color change through increasing levels even for under 10 ppm so I thought it would be a good choice. My levels were consistantly 2.5 which seemed too low especially with the amount of fish in the tank. So I mixed up a standard solution based on the FAQ here and aimed for 10ppm of Nitrate. The test still read about 2.5 or less. So much for measurements. So I broke down and bought a Lamotte kit. Readings are about 22ppm of nitrate, between 4 and 6 on the color comparitor of NO3-N which is what the Lamotte kit reports. So at least for my Red Sea Nitrate test kit the results seem way too low. I am also getting pretty low PO4 levels with a Red Sea test kit. Now I have to check that one as I suspect it may also be falsely low.

Stuart


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## HeyPK (Jan 23, 2004)

I have a number of LaMotte kits and I find that they are accurate and worth the money. I have not had personal experience with Red Sea, but I do recall seeing some complaints about their accuracy.


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## Left C (Jun 14, 2005)

Stuart, this might help you to test the accuracy of your test kits.

*How to Make Reference NO3 and PO4 Solutions *

Here's a way to make 10, 20, 30 and 40 ppm NO3 reference solutions:

Add 1.631 g of KNO3 to 1 L distilled or DI water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of distilled or DI water. This makes 20 mL of a 100 ppm NO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of distilled or DI water. This makes 30 mL of a 50 ppm NO3 solution.

_To make a 10 ppm NO3 solution:_
Add 2 mL of the 50 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 10 ppm NO3 solution.

_To make a 20 ppm NO3 solution:_
Add 4 mL of the 50 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 20 ppm NO3 solution.

_To make a 30 ppm NO3 solution:_
Add 6 mL of the 50 ppm solution to 4 mL of distilled or DI water. This makes 10 mL of a 30 ppm NO3 solution.

_To make a 40 ppm NO3 solution:_
Add 8 mL of the 50 ppm solution to 2 mL of distilled or DI water. This makes 10 mL of a 40 ppm NO3 solution.

Here's a way to make 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

Add 1.433 g of KH2PO4 to 1 L of distilled or DI water. This makes a 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of distilled or DI water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of distilled or DI water. This makes 20 mL of a 10 ppm PO4 solution.

_To make a 1.0 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 9 mL of distilled or DI water. This makes 10 mL of a 1.0 ppm PO4 solution.

_To make a 2.0 ppm PO4 solution:_
Add 2 mL of the 10 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 2.0 ppm PO4 solution.

_To make a 3.0 ppm PO4 solution:_
Add 3 mL of the 10 ppm solution to 7 mL of distilled or DI water. This makes 10 mL of a 3.0 ppm PO4 solution.

_To make a 4.0 ppm PO4 solution:_
Add 4 mL of the 10 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 4.0 ppm PO4 solution.

_To make a 5.0 ppm PO4 solution:_
Add 5 mL of the 10 ppm solution to 5 mL of distilled or DI water. This makes 10 mL of a 5.0 ppm PO4 solution.


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## Edward (May 25, 2004)

Hi 
A test kit 'calibration' is easy with your PPS-Pro macro solution, as per APC FAQ. Any known tap water is fine.

*NO3*
25 drops in 10 litre = 5 ppm
2 ml and 10 drops or 50 drops in 10 litre = 10 ppm
5 ml in 10 litre = 20 ppm
7 ml and 10 drops in 10 litre = 30 ppm
10 ml in 10 litre = 40 ppm
12 ml and 10 drops in 10 litre = 50 ppm

*PO4*
5 drops in 10 litre = 0.1 ppm
10 drops in 10 litre = 0.2 ppm
25 drops in 10 litre = 0.5 ppm
50 drops or 2 ml and 10 drops in 10 litre = 1 ppm
5 ml in 10 litre = 2 ppm

Personally, I use regular cheap LFS Hagen Nutrafin test kits. You 'calibrate' the product line just once to understand the colour chart, that's it. No need to repeat this with every other kit you buy. 

Thank you
Edward


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## sc204 (Nov 17, 2007)

Thanks I did use the concentrations from the FAQ to test the test kit. My Red Sea kit seemed really off so I didn't try to make a calibration. It really seems useless in the lower range which is where I want the accuracy.

Thanks Left C, I like your mixes better. 10 l is a lot of water to mix up 

I still need to calibrate the phosphate kit. 

Thanks,
Stuart


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## Edward (May 25, 2004)

sc204 said:


> It really seems useless in the lower range which is where I want the accuracy.
> 
> Thanks Left C, I like your mixes better. 10 l is a lot of water to mix up


Well, think about practicality and final accuracy. For example, how do we get exactly 1.433 grams? Then we add 1 ml to 9 ml, then 2 ml to 18 ml, then 1 ml to 9 ml just to get 1 ppm of PO4? You know how inaccurate this is? And at this point we still don't have 0.5, 0.2 and 0.1 ppm of PO4. 

Everybody got one of these 











and plenty of tap water to use accurately and reliably. Most people already have the macro solution and if not then it is easy to get just 6 grams into 1 liter.


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## Left C (Jun 14, 2005)

Edward said:


> Hi
> A test kit 'calibration' is easy with your PPS-Pro macro solution, as per APC FAQ. Any known tap water is fine.
> 
> *NO3*
> ...


You aren't using the PPS-Pro solution for this.

You are using the PPS Classic SS solution for this. Isn't this correct? http://www.aquaticplantcentral.com/...utrients-facts-interactions-deficiencies.html

Here's the differences:

PPS Classic SS in 500 ml
K2SO4 - 16 grams
KNO3 - 20 grams
KH2PO4 - 6 grams

PPS Pro macro in 1 L
K2SO4 - 54 grams
KNO3 - 65 grams
KH2PO4 - 6 grams
MgSO4∙7H2O - 41 grams

Like sc204 mentioned 10L or 2.642 gallons is a lot to use to make for testing a test kit.

To do it completely accurately, you really need to add the amounts of the solvents to a fresh 10L of distilled water. This is a bunch of water. But, in actuality, you can remove a small amount of the solution to test your test kit and just keep adding the solvent to it. You won't be wrong by much at all.


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## Left C (Jun 14, 2005)

Edward said:


> Well, think about practicality and final accuracy. For example, how do we get exactly 1.433 grams? Then we add 1 ml to 9 ml, then 2 ml to 18 ml, then 1 ml to 9 ml just to get 1 ppm of PO4? You know how inaccurate this is?


Edward

This is much more accurate than you saying that there is 4L in 1 gallon when there really is 3.785L in 1 gallon.

It's also much more accurate than you saying MgSO4∙7H2O is the same thing as MgSO4.

I don't know about you, but I have access to scales that can measure to 6 decimal places. Weighing to 3 decimal places is easy. Don't you have access to a decent set of scales?

I don't know about you, but I can add 1 ml to 9 ml accurately. Can't you?

I don't know why you are saying that this is inaccurate. I do this and more everyday in lab.



Edward said:


> And at this point we still don't have 0.5, 0.2 and 0.1 ppm of PO4.


Here you go for this part.

_To make a 0.5 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 19 mL of distilled or DI water. This makes 20 mL of a 0.5 ppm PO4 solution.

_To make a 0.2 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 49 mL of distilled or DI water. This makes 50 mL of a 0.2 ppm PO4 solution.

_To make a 0.1 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 99 mL of distilled or DI water. This makes 100 mL of a 0.1 ppm PO4 solution.



Edward said:


> Personally, I use regular cheap LFS Hagen Nutrafin test kits. You 'calibrate' the product line just once to understand the colour chart, that's it. No need to repeat this with every other kit you buy.


The color casts for the printed Hagen color charts are very bad. This is especially true for their phosphate test kits. The color charts were printed using a red cast blue dye instead of a green cast blue dye. This makes it very hard match the colors.

I think that one of the better things to do is to get very good quality test kits like the LaMotte as HeyPK suggested.

Thanks,
Left C


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## MatPat (Mar 22, 2004)

For some one new to the hobby I have to agree with the LaMotte kits. For some, it is much easier to spend a little more money to get an accurate kit than it is to make some calibration solutions. Most folks worry about adding the chemicals to their tanks let alone making up solutions to calibrate those test kits. 

I have always had trouble reading those color charts but the LaMotte kits make it very easy since a colorimeter is included with the kits. Just insert the test tube and figure out how closely it measures the colored liquid to the side of the tube. Very simple. A few years ago, each new Seachem kit I ordered had a color chart that was a bit different color than the previous kit. If you are calibrating solutions to a color chart, which one should you use, a separate calibration for each, to train your eye?

For those with more "experience" it's not very difficult to make a known solution to calibrate a test kit. But for a beginner, that task can seem out of reach most of the time.


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## Edward (May 25, 2004)

Left C said:


> Edward
> 
> I don't know about you, but I have access to scales that can measure to 6 decimal places. Weighing to 3 decimal places is easy. Don't you have access to a decent set of scales?
> 
> ...


 No one is talking about you Left C and your professional laboratory. We are sure you can measure it perfectly to 6 decimal places, but this forum is mostly for hobbyists and getting precisely *1.433000* grams at home is not that easy, don't you agree?


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## sc204 (Nov 17, 2007)

I started this thread so I will add my 2 cents from someone who is a little more than the average hobbyist. I may be a NUBE at plants but I have been raising fish for a long time including having a 3000 gallon angel hatchery for about 5 years. 

Scales: I have 2 one measures to .1 gm and costs about $200 now and the other to 1 gm and costs less than $40 on Ebay including shipping. The less accurate one measures to 5 Kg which I needed for my other hobby, R/C planes. I would suspect that anyone in this hobby could afford the scale that measures to 1 gm but most would not want to spend the money on the more accurate one. Most do not have availability of a lab with more accurate scales. Some do but nost wouldn't or would prefer not to have to travel to a lab to make a measurement. 

Volume: 10 liters of distilled or R/O osmosis water is a lot if you do not have an R/O system. 1 Liter would be much more managable. Most people can also measure out 1 cc to mix into 20 etc. 

Drops are also not my favorite measurment as the size of the drop can vary depending on the diameter of the tip of the dropper. I know IV tubing has drop sizes that run from 10 to 60 drops per cc.

Stuart


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## sc204 (Nov 17, 2007)

So I was thinking of how to make a simple solution to test the accuracy of a kit. I want to make a test solution of about 1.5 ppm of PO4. Using the Fertilator (It is accurate, right?) 2 gms which I can measure to a tenth of a gram so I should be within 5% added to 1 liter of distilled or R/O water is equal to 1396 ppm. Dilute that by 1000 to 1 and you get 1.396 ppm or about 1.4 ppm. 1.07cc diluted to 1000 cc would give me my 1.5ppm test solution. 1.07 cc can be measured using an insulin syringe. With standard measurment tools I should be able to be within 10% (and maybe closer) which is good enough. My Red Sea NO3 test kit was off by a factor of 10 

Does this make sense?
Stuart


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## sc204 (Nov 17, 2007)

I'll respond to my own post again 

I made the standard above for phosphate and one for nitrate starting with 2 grams pot nitrate and 2 grams of KH2PO4 in 1 liter of distilled water. 1.07 cc was diluted to 1 l for the PO4 standard and 7.18cc was diluted to 1 liter for the nitrate standard of 8.8 ppm NO3. The Lamotte kit measures in NO3-N so I was trying to match the 2.0 color. (NO3-N in ppm * 4.4 = NO3 in ppm)

My RS PO4 test kit read under .1 ppm while the Lamotte kit (bought because the RS kit was always reading low) was right on at 1.5ppm.

For Nitrate the RS kit read between 0 and 2.5 wjile the Lamotte was just above 2ppm NO3-N. Definitely under the next color of 4.0

There are obvioulsy some good test kits out there and some that are not too accurate. I would agree and reccomend to anyone basing their dosing on test kits to run a standard at about the level you are aiming for.

Stuart


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## Left C (Jun 14, 2005)

Edward said:


> No one is talking about you Left C and your professional laboratory. We are sure you can measure it perfectly to 6 decimal places, but this forum is mostly for hobbyists and getting precisely *1.433000* grams at home is not that easy, don't you agree?


Hi Edward

You're right. I have access to the chemistry, biology and biotechnology labs at the college here. It's easy for me to do things.

But, you can still use these same formulas by moving the decimal place one place to the right for the very first step if your scales will measure to 2 decimal places. So use 14.33 grams and not 1.433 grams as an example. You'll be using 10L of water instead of 1L for the first step. The other steps will be the same.

_*Edit: Here's a better solution if you have scales that measure to no decimal place or one decimal place in grams.*

You can measure 10.0 grams of KNO3 to 6.13 L of distilled water or 5 grams to 3065 mL of distilled water in the first step for the first step in the KNO3 solution. This gives you a 1000.49 ppm NO3 solution to start with. Follow the rest of the steps as listed.

You can measure 5.0 grams of KH2PO4 to 3.49 L of distilled water or 2.5 grams to 1745 mL of distilled water in the first step for the first step in the KH2PO4 solution. This gives you a 999.86 ppm PO4 solution to start with. Follow the rest of the steps as listed._

Ebay has decent digital scales that will weigh grams to 2 decimal places for around $20 or less. 100g x 0.01g would be my first choice, but 50g x 0.01g will work too.
http://search.ebay.com/search/searc...ftrt=1&ftrv=1&saprclo=&saprchi=&fsop=1&fsoo=1

Left C

PS: Again, if you want to test your water accurately, get very good quality test kits like Lamotte, Hach, etc.

I use Seachem's Phosphate and Nitrite/Nitrate test kits because they come with reference solutions. The color card is hard to use. There's such a gradual change in the depth of the color for the ppm changes. Printing errors can make this even worse. About all I can do is to see if it is calibrated fairly close and when I test my aquarium water; all I know is if I have too little, too much or just about right concentrations. I can't give you the exact ppm at all.


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## Left C (Jun 14, 2005)

I rewrote these directions to help the people that have scales that measure to no decimal place or to one decimal place. This is better for the average hobbyist or people that don't have access to scales that can measure to two, three or more decimal places. I hope that this is easier to do and that it helps the people that want to calibrate their NO3 and PO4 test kits.

*How to Make Reference NO3 and PO4 Solutions II*

Here's a way to make 10, 20, 30, 40 and 50 ppm NO3 reference solutions:

_Note - This step requires that you have scales that can measure to 3 or more places._ Add 1.631 grams of KNO3 to 1 L distilled or DI water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm NO3 solution.)

_If you have scales that measure to no decimal place or one decimal place in grams; here's two options. Omit the above step and start here:_
Add 10.0 grams of KNO3 to 6.13 L of distilled or DI water or 5 grams to 3065 mL of distilled or DI water. This makes the 1000 ppm NO3 solution. (It's really a 1000.49 ppm NO3 solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of distilled or DI water. This makes 20 mL of a 100 ppm NO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of distilled or DI water. This makes 30 mL of a 50 ppm NO3 solution. _You can use this for the 50 ppm NO3 reference solution._

_To make a 10 ppm NO3 solution:_
Add 2 mL of the 50 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 10 ppm NO3 solution.

_To make a 20 ppm NO3 solution:_
Add 4 mL of the 50 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 20 ppm NO3 solution.

_To make a 30 ppm NO3 solution:_
Add 6 mL of the 50 ppm solution to 4 mL of distilled or DI water. This makes 10 mL of a 30 ppm NO3 solution.

_To make a 40 ppm NO3 solution:_
Add 8 mL of the 50 ppm solution to 2 mL of distilled or DI water. This makes 10 mL of a 40 ppm NO3 solution.

Here's a way to make 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

_Note -This step requires that you have scales that can measure to 3 or more places._ Add 1.433 g of KH2PO4 to 1 L of distilled or DI water. This makes the 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution PO4.)

_If you have scales that measure to no decimal place or one decimal place in grams; here's two options. Omit the above step and start here:_
Add 5.0 grams of KH2PO4 to 3.49 L of distilled or DI water or 2.5 grams of KH2PO4 to 1745 mL of distilled or DI water. This makes the 1000 ppm PO4 solution. (It's really a 999.86 ppm PO4 solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of distilled or DI water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of distilled or DI water. This makes 20 mL of a 10 ppm PO4 solution.

_To make a 0.1 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 99 mL of distilled or DI water. This makes 100 mL of a 0.1 ppm PO4 solution.

_To make a 0.2 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 49 mL of distilled or DI water. This makes 50 mL of a 0.2 ppm PO4 solution.

To make a 0.5 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 19 mL of distilled or DI water. This makes 20 mL of a 0.5 ppm PO4 solution.

_To make a 1.0 ppm PO4 solution:_
Add 1 mL of the 10 ppm solution to 9 mL of distilled or DI water. This makes 10 mL of a 1.0 ppm PO4 solution.

_To make a 2.0 ppm PO4 solution:_
Add 2 mL of the 10 ppm solution to 8 mL of distilled or DI water. This makes 10 mL of a 2.0 ppm PO4 solution.

_To make a 3.0 ppm PO4 solution:_
Add 3 mL of the 10 ppm solution to 7 mL of distilled or DI water. This makes 10 mL of a 3.0 ppm PO4 solution.

_To make a 4.0 ppm PO4 solution:_
Add 4 mL of the 10 ppm solution to 6 mL of distilled or DI water. This makes 10 mL of a 4.0 ppm PO4 solution.

_To make a 5.0 ppm PO4 solution:_
Add 5 mL of the 10 ppm solution to 5 mL of distilled or DI water. This makes 10 mL of a 5.0 ppm PO4 solution.


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## BryceM (Nov 6, 2005)

Back to the OP's question, I'm going to make the assumption that if you have the financial resources for a 900g planted tank then you should be able to afford good quality test kits. I'll second what others have said concerning Lamotte's kits. Their value comes from two things they do better than their competitors. The first is that their color comparitors are generally better and easier for most of us to use. The second is that their reagents are produced to much stricter standards with better quality control. The majority of their users are using their products for industrial or municipal purposes. Makers of hobby-grade kits have little incentive to meet such exacting standards. It basically comes down to "you get what you pay for".

If I was truly serious about testing I'd use something even a step up from Lamotte's basic test kits. I'd get an electronic colorimeter that self-calibrates and self-tests against blanks. Lamotte has one example called the Smart2 colorimeter. The actual test procedures and reagents are identical to their basic test kits, but the electronic unit is far better at analyzing the resulting color and can give accurate readings out to a decimal point or two for most of the things we're looking at.

Now, I don't use one, and to be honest, it's almost never necessary to be this precise for our purposes, but it might be useful for someone who is truly interested in the effect of different nutrient levels. It probably should be used by anyone reporting their results as gospel truth.

In my experience, (having spent a few years in a water quality lab) using test kits goes something like this:

*Hobby grade* - you're usually better off to not test at all, since the results are suspect, at best. If you don't understand their limitations, the so-called "results" will often cause you to do something foolish. Bad information is worse than no information at all.

*Lamotte basic grade* - you still need an understanding of the limitations of the chemistry behind the tests. Non-contaminated, fresh reagents are needed to produce accurate results. Tests should still be occasionally compared to known standards to ensure you're testing what you think you are. These tests are guaranteed accurate when testing for the desired compound when it alone is present in pure water. Lamotte's nitrate kit is affected by nitrite and ammonia, etc. etc.

*Lab grade* - Actual accredited water quality laboratories are very careful to ensure that their tests actually measure what they think they do. They run controls on a daily basis and they are monitored by outside review on a regular basis. You pay extra, but the results actually mean something.

Also, don't rely too much on a city's water report. Usually this is something they print out for a given sample on a given day. Many cities use different water sources at different times of the year (lake, river, deep well). When you go to make your "standard solutions" don't forget that your particular tap water might already be loaded with phosphates or nitrates, especially in agricultural areas.

Just because one person has success doing something a particular way doesn't mean that their methods will be universally applicable.

End of rant......


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## hoppycalif (Apr 7, 2005)

Guaiac Boy, that is a very good primer on testing in aquariums! We should all read it!


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## Gilles (Oct 12, 2007)

Left C said:


> Stuart, this might help you to test the accuracy of your test kits.
> 
> ...How to Make Reference NO3 and PO4 Solutions...


I always thought that adding 1 gram of NO3 to 1000l gives 1000mg, not 1.433 grams..
- Why the difference?


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## Left C (Jun 14, 2005)

Gilles said:


> I always thought that adding 1 gram of NO3 to 1000l gives 1000mg, not 1.433 grams..
> - Why the difference?


Hi Gilles

I'm not quite sure what you're asking? 1000mg? Are you meaning to say 1000 ppm.

You may be confused a little. The 1.433 grams is for the PO4 reference solutions using KH2PO4. It's not the amount used in making a NO3 reference solution.



Gilles said:


> - If you don't have a milligram scale, for instance only 1,2,3 grams.. How much water do you need then? 2L for 3 grams?


This is answered in the lasted version of *How to Make Reference NO3 and PO4 Solutions II*. See post #15.

_If you have scales that measure to no decimal place or one decimal place in grams; here's two options. Omit the above step and start here:_
Add 10.0 grams of KNO3 to 6.13 L of distilled or DI water or 5 grams to 3065 mL of distilled or DI water. This makes the 1000 ppm NO3 solution. (It's really a 1000.49 ppm NO3 solution.)

_If you have scales that measure to no decimal place or one decimal place in grams; here's two options. Omit the above step and start here:_
Add 5.0 grams of KH2PO4 to 3.49 L of distilled or DI water or 2.5 grams of KH2PO4 to 1745 mL of distilled or DI water. This makes the 1000 ppm PO4 solution. (It's really a 999.86 ppm PO4 solution.)

I hope this helps you.

Left C


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## Gilles (Oct 12, 2007)

Left C said:


> I'm not quite sure what you're asking? 1000mg? Are you meaning to say 1000 ppm.


Yep, sorry for that.



Left C said:


> You may be confused a little. The 1.433 grams is for the PO4 reference solutions using KH2PO4. It's not the amount used in making a NO3 reference solution.


Yep that is what i meant. Why do we need to add 1.433 of KH2PO4 and not just 1 gram to 1000ppm?

P.s. just bought a scale that goes to 0.01 grams for 20$


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## BryceM (Nov 6, 2005)

If you're trying to make a *KNO3* reference solution then add 1 gram KNO3 to 1000 ml of water. If you are trying to make an *NO3-* reference solution, you need to add more, since you need to account for the mass of the potassium. Using the ratio of atomic weights, it turns out that 1.631 grams of KNO3 in 1 liter of water is needed to produce a 1000 ppm NO3- reference solution.


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## Left C (Jun 14, 2005)

Gilles said:


> Yep, sorry for that.
> 
> Yep that is what i meant. *Why do we need to add 1.433 of KH2PO4 and not just 1 gram to 1000ppm?*
> 
> P.s. just bought a scale that goes to 0.01 grams for 20$


B]Why do we need to add 1.433 of KH2PO4 and not just 1 gram to 1000ppm?[/B]

Good gosh Gurtie, what a gash!

This isn't 1000 ppm is it? Don't you mean 1000 mL or 1 L?

If you add only 1 gram of KH2PO4 to 1000 ml: this equals 697.9 ppm of PO4. My instructions make a 1000.09 ppm PO4 solution to start with. This will make the rest of the dilutions wrong and not usable to use for reference solutions given the instructions that I have.

If you want to play with the math some, use 1 gram of KH2PO4 in fertilator and see how many mL of distilled or DI water to add to make a 1000 ppm PO4 solution.

Well, I've already did it. 1.0 gram of KH2PO4 added to 697.9 mL of distilled or DI water gives you a 1000 ppm of PO4 to start with. Then just follow the rest of the instructions.

Anyway, there's more than one way to "skin a cat." All you have to do is to just play with the numbers some to come up with different dilution recipes. There's really an almost infinite way to do them.


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## Left C (Jun 14, 2005)

Hi Mods and everyone.

I made a typo in the fourth paragraph in my post that is *How to Make Reference NO3 and PO4 Solutions II*. It's post #15. The last sentence should say 50 ppm and not 50 ml.

This is the way that it should read:

Add 15 mL of the 100 ppm solution to 15 mL of distilled or DI water. This makes 30 mL of a 50 ppm NO3 solution. _You can use this for the 50 ppm NO3 reference solution._

Would one of the mods be so kind to correct this for me. It won't let me edit it.

Thanks,
Left C


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## MatPat (Mar 22, 2004)

Left C said:


> Hi Mods and everyone.
> 
> I made a typo in the fourth paragraph in my post that is *How to Make Reference NO3 and PO4 Solutions II*. It's post #15. The last sentence should say 50 ppm and not 50 ml.
> 
> ...


Done, please double check that I cut and pasted the info in the right place


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## Left C (Jun 14, 2005)

Thanks MatPat!

That's the right place. I really appreciate it.

Left C


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## Gilles (Oct 12, 2007)

Thanx for explaining Left-C, i am from the Netherlands and just starting to dose the right ammounts of KNO3 and PO4.


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## Left C (Jun 14, 2005)

You're very welcome Gilles


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## felixm (Jan 20, 2007)

MatPat,
Thanks for the redirect to this thread. Where can you get KNO3 or NO3 or any of the chemicals to make these test solutions?


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## MatPat (Mar 22, 2004)

For the best prices you can try sending Turbomrkt a PM and asking him for KNO3 and KH2PO4. He ships fast and is very easy to work with. I'm not sure how small of a quantity he will send but if you plan on fertilizing, these are the same things you would use to add NO3 and PO4 to your tank. 

I'm not sure if we have a sponsor selling dry ferts any longer.


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## Left C (Jun 14, 2005)

Seachem's Nitrite/Nitrate and Phosphate test kits come with reference solutions. The Nitrate test kit comes with a 10.0 ppm NO3 reference solution and the Phosphate test kit comes with a 1.0 ppm PO4 reference solution.
http://www.seachem.com/products/testkits.html


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## felixm (Jan 20, 2007)

MatPat, 
I could not find sponsors selling ferts.


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