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Old 12-21-2007, 06:57 PM   #1 (permalink)
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Default Test kit accuracy

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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Old 12-22-2007, 08:25 AM   #2 (permalink)
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Default Re: Test kit accuracy

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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Old 12-22-2007, 05:05 PM   #3 (permalink)
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Default Re: Test kit accuracy

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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Old 12-24-2007, 07:37 AM   #4 (permalink)
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Default Re: Test kit accuracy

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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Old 12-24-2007, 08:53 AM   #5 (permalink)
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Default Re: Test kit accuracy

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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Old 12-25-2007, 06:06 AM   #6 (permalink)
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Default Re: Test kit accuracy

Quote:
Originally Posted by sc204 View Post
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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Old 12-26-2007, 10:17 PM   #7 (permalink)
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Default Re: Test kit accuracy

Quote:
Originally Posted by Edward View Post
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
You aren't using the PPS-Pro solution for this.

You are using the PPS Classic SS solution for this. Isn't this correct? https://www.aquaticplantcentral.com/f...iciencies.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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Old 12-26-2007, 11:01 PM   #8 (permalink)
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Default Re: Test kit accuracy

Quote:
Originally Posted by Edward View Post
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.



Quote:
Originally Posted by Edward View Post
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.



Quote:
Originally Posted by Edward View Post
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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Old 12-28-2007, 11:37 AM   #9 (permalink)
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Default Re: Test kit accuracy

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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Old 12-28-2007, 01:49 PM   #10 (permalink)
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Default Re: Test kit accuracy

Quote:
Originally Posted by Left C View Post
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?

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.


Thanks,
Left C
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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