.Nitrate measurement for tanks....2004
How reliable are the nitrate test available in Europe and how is their reading precision ?

Already two years ago our nitrate test evaluation caused a stir. Some hobbyist came together and evaluated the at that time relevant nitrate test kits. As it is now two years ago we decided to repeat the evaluation. There are now new test kits available and on the other hand we wanted to know if the manufactures of the previous tested kits have improved their quality. In collaboration with Sabine and Harald Mülder, Thomas Chronz and Markus Leiser, we started the "Nitrate Test Evaluation 2004" on 21.02.2004.

Preparations...by Markus Leiser

We always had  www.Meerwasserforum.com next to us on the Laptop:-)

Markus Leiser ordered a nitrate parent solution from Merck (Batch number:1.19811.0500)

This solution had exactly 1000mg nitrate per liter. Specific gravity of this dilution has been verified by alkalimetric titration. The water has been measured by 20 degree (Calibration temperature of pipettes and measuring glass) and the respectively needed amount of the parent solution has been added to the dilution 1,2 and 3.

We used LicroSolv which is purest water used for chromatography. Afterwards we set the salinity to 35 per thousand and verified the result with an refractometer. All measurements have been taking at room temperature. We took care the there was no daylight incidence on the measuring glass.

We used Tropic Marin salt which had been purchase three weeks ago. All test have been performed with the equipment which belongs to the test kit!  The test kits have been provided free of charge form the following pet stores / online stores: Mrutzek Meeresaquaristik donated the JBL and Tetra test kit, Claude Schuhmacher donated the test kits from: Red Sea, Tropic Marin, Salifert, Machery & Nagel Visocolor Eco Neu, Andreas Neufeld brought the new Aqualight Nitrate Test. Markus Leiser brought the Aquanal Nitrattest from Riedel-de-Haen, Robert purchased the tow test kits from Nutrafin and Sera at Welke Lünen, who where so kind to give him 20% discount. We like to thank everybody for enabling us to use the different test kits.

The following NO3 test kits have been evaluated:


Manufacturer Batch number Expires max test Range Price
RED SEA 23 23.05.05 60 Tests High Range: 0-12,5-25-50-100-250
Low Range:  0-2,5-5,0-10-20-50
ca. 14,00 €
SALIFERT N03-1 T0308
N03-2 NB-B 2642
N03 Me-059
K.A. 60 Tests Normal:0-2-5-10-25-50-100
Accurate: divide by 10 
ca. 10,00 €
TETRA 326989 Ce  T616 K.A. K. A. 0-12,5-25-50-100 ca. 11.20 €
NUTRAFIN/Hagen Dilution 1: Lot A10
Dilution 2: Lot Ao9
Dilution 3: Lot Ao9
30.04.2005 80 Tests 5-10-20-50-110 ca. 14,00 €
JBL 09849702 - 50 Tests 0-1-5-10-20-40-60-80-120-160-240 ca. 14.80 €
AQUALIGHT - - 50 Tests 5-10-20-40-60-100 ca. 10,00 €
TROPIC MARIN - 30.05.2005 40 Tests -1-5-10-20-50-100 ca. 14,00 €
SERA CH6  03 11-2008 60 Tests 0-5-10-20-40 - 400 je nach Höhe No3 ca.   9,00 €
Aquanal Plus
Lot 10920 02.04.2004 200 Tests 1-2-3-5-10-20-35-50  1-50 mg/L
Photometrisch 0,5 - 50 mg/L
ca. 55,00 €
Visocolor Eco NEU
Lot 1021 10-2005 110 Tests 0-1-3-5-10-20-30-50-70-90-120 ca. 33,00 €
Visocolor Eco Old
Lot 0190 03-2005 110 Tests 0-4-10-20-30-50-70-90-120 ca. 33,00 €
Harald Mülder and Markus Leiser made the three reference dilutions with different nitrate concentration. Only they knew which dilution had which nitrate level. Due to this the four test persons did not know the nitrate concentration of the three different dilutions. The test it self was prepared by one person, the determination of the result has been made by four different persons.

As one can see in the following people read the color codes different. Therefore this is already the cause for some variations of the results. This year we did not  use the photometer from Hanna as they meanwhile announced that their tool is not to be used for nitrate determination of salt water.


Dilution 1 contained 4 mg Nitrate
Dilution 2 contained 18 mg Nitrate
Dilution 3 contained 40 mg Nitrate


Manufaturer Dilution 1 (4 mg)  Dilution 2 (18 mg)  Dilution 3 (40 mg)
RED SEA Tester1   0 
Tester2   0
Tester3   0
Tester4   0
Tester1   0
Tester2   0
Tester3   0
Tester4   0
Tester1   0
Tester2   0
Tester3   0
Tester4   0
SALIFERT Tester1  3,0 mg
Tester2  2,5 mg
Tester3  2,5 mg
Tester4  2,5 mg
Tester1  12,0 mg
Tester2  10,0 mg
Tester3  10,0 mg
Tester4  10,0 mg
Tester1  35,0 mg
Tester2  40,0 mg
Tester3  40,0 mg
Tester4  40,0 mg
TETRA Tester1  12,0 mg
Tester2  10,0 mg
Tester3  10,0 mg
Tester4  10,0 mg
Tester1  20,0 mg
Tester2  20,0 mg
Tester3  20,0 mg
Tester4  22,0 mg
Tester1   75,0 mg
Tester2   60,0 mg
Tester3   50,0 mg
Tester4   75,0 mg
HAGEN Tester1   5,0 mg
Tester2   5,0 mg
Tester3   5,0 mg
Tester4   5,0 mg
Tester1   5,0 mg
Tester2   5,0 mg
Tester3   5,0 mg
Tester4   5,0 mg
Tester1    5,0 mg
Tester2    5,0 mg
Tester3    5,0 mg
Tester4    7,0 mg
JBL Tester1   1,0 mg
Tester2   1,0 mg
Tester3   1,0 mg
Tester4   1,0 mg
Tester1  10,0 mg
Tester2  10,0 mg
Tester3  12,0 mg
Tester4  15,0 mg
Tester1   20,0 mg
Tester2   20,0 mg
Tester3   20,0 mg
Tester4   20,0 mg
AQUALIGHT Tester1   1,0 mg
Tester2   2,0 mg
Tester3   1,0 mg
Tester4   2,0 mg
Tester1  10,0 mg
Tester2  10,0 mg
Tester3  10,0 mg
Tester4  10,0 mg
Tester1   15,0 mg
Tester2   10,0 mg
Tester3   12,0 mg
Tester4   10,0 mg
TROPIC MARIN Tester1   1,0 mg
Tester2   1,0 mg
Tester3   2,0 mg
Tester4   2,0 mg
Tester1  10,0 mg
Tester2  10,0 mg
Tester3  10,0 mg
Tester4  10,0 mg
Tester1   20,0 mg
Tester2   15,0 mg
Tester3   20,0 mg
Tester4   15,0 mg
SERA Tester1   5,0 mg
Tester2   5,0 mg
Tester3   5,0 mg
Tester4   5,0 mg
Tester1  n.a. 
Tester2  40,0 mg
Tester3  40,0 mg
Tester4  30,0 mg
Tester1    80,0 mg
Tester2    80,0 mg
Tester3    80,0 mg
Tester4    80,0 mg
MACHERY-NAGEL NEU Tester1   2,5 mg
Tester2   2,5 mg
Tester3   2,5 mg
Tester4   2,5 mg
Photomet. 5,0 mg
Tester1    8,75 mg
Tester2    8,75 mg
Tester3    8,75 mg 
Tester4  10,00 mg
Photomet. 8,75 mg
Tester1    18,75 mg 
Tester2    18,75 mg
Tester3    22,00 mg
Tester4    18,75 mg
Photomet.26,25 mg 
RIEDEL-DE-HAEHN Tester1   3,0 mg
Tester2   3,0 mg
Tester3   3,0 mg
Tester4   3,0 mg
Photometer 4 mg
Tester1     5,0 mg
Tester2   10,0 mg 
Tester3   10,0 mg
Tester4     5,0 mg
Photomet. 14,3 mg
Tester1    50,0 mg
Tester2    50,0 mg
Tester3    50,0 mg
Tester4    35,0 mg
Photomet. 36,0 mg
MACHERY-NAGEL ALT Tester1   5,0 mg 
Tester2   5,0 mg
Tester3   5,0 mg
Tester4   5,0 mg
Tester1   18,75 mg
Tester2   25,00 mg
Tester3   18,75 mg
Tester4   18,75 mg
Tester1   37,50 mg
Tester2   37,50 mg
Tester3   37,50 mg
Tester4   37,50 mg

It was almost impossible to read the expiration date of the Red Sea test. One of the test bottles containing reagent C was already damaged as we open the test kit. Performing the test we faced that no results could be achieved. obviously the bottle got damaged and the reagent. Therefore we could not evaluate this test.  Kindly refer to our evaluation two years ago - there the test kit scored very good.

This test is new on the market and we where looking forward to see its performance. Unfortunately the test did not meet our requirements in terms of handling, result determination and accuracy. Very disappointing was the spatula where we really ask our self how one can measure the correct amount reagent. Aqualight should work on this..

The Marin Test Kit convinced with the usual good handling and the color scale to determine the result was easy to read. But the test was not as accurate as we expected.

Color scales are easy to read. But in the higher nitrate levels it shows almost the double of the real concentration.

With Tetra you can only see a vague tendency, in the lower and higher nitrate range it showed to much and in the middle range it showed roughly the correct values. The color scale is not bad and intensive.

No comment .... see table above

JBL shows a tendency which is getting more inaccurately as higher the nitrate concentration gets.

Salifert shows a accurate tendency which is getting more accurate in the higher levels. Has a good cost / performance ration.

People had problems to determine the correct color scale with artificial light. No other test has been compared that long. That's one of the reason why the different people has different results. But this test is currently hardly know in our hobby.

Recently Machery-Nagel changed the color scale to enable better results. We don't know, if the test it self has been changed too. It was significant that the new test did not even approximately reach the expected good results as  the "old" test did.

As the new version showed so bad results we took the old test out of our drawer. It has expiration date March 2005. This test kit showed the best results of all evaluated test kits. The color scale was very good to read and is was easy to determine the result. That's how we expect a test to be. Feel lucky if you still own one of this series. It would be interesting to know why the new version showed so bad results

After the unexpected bad results of the MN test kit we contacted  Machery-Nagel as this test is currently the sate of the art thet not only for  reefers.
Dr. Reinhardt, form Machery-Nagel stated that the only reason he could imagine would be the powder.  Claude Schuhmacher did send us a new MN test kit from the same batch 1021 and a Red Sea test kit so that we could make up that test as the first one was not usable (see above)
On February 28th Sabine und Harald Mülder started the comparative test.  For comparison they used an about one year old MN test which has been used already several times. This might explain the slight deviations.

Manufaturer Dilution 1 (4 mg) Dilution 2 (18 mg) Dilution 3 (40 mg)
RED SEA Tester1: nicht ablesbar
Tester2: nicht ablesbar
Tester 1:  2,5 mg
Tester 2:  2,5 mg
Tester 1:  5,00 mg
Tester 2:  5,00 mg
Machery-Nagel NEU
Charge 1021 
1,00 mg  7,5 mg 18,75 mg
Machery-Nagel NEU
Charge 1021 
Pulver alter Test
1,00 mg  7,5 mg 18,75 mg
Machery-Nagel ALT
Charge 0190
3,75 mg 15,00 mg 31,25 mg

So we have to point out that also the second test showed to less and therefore wrong values.  Meanwhile we figured out that what is most likely the reason.  It is not the powder as expected form Machery-Nagel , it seems to be liquid 1.  Because if we used the liquid 1 from the old test kit we could achieve more reliable test results with the new powder.

We also have an addendum to the Tetra test kit.  Sabine Mülder discovered that if you keep a little more distance between the test cylinder and the color scale the values seem the be a little lower and therefore more close to to correct values.  Still not exact but better than holding the test cylinder directly in front of the color scale. . Unfortunately there is not hint like that on the user manual.

The winner of the first Nitrate Test benchmarking Red Sea did not reach the expectations during this second comparative test at all. Machery-Nagel should definatly check again the batch 1021 and verify what is wrong.  Finally only the test from Salifert comes up with an reasonable result.  We are very very disappointed that only one of the manufacturers seems to be able to produce a reliable test.

We want to thank Mrs. Leiser for supporting us with food and beverages so that we did not have to suffer from thirst or hunger  :-)

Final conclusion:
we are excessively disappointed what some manufactures sell us as a nitrate test. We could have bought a dice box and "determine" the nitrate like this ...

Sabine Mülder, Harald Mülder Thomas Chonz, Markus Leiser, Manuela Kruppas and Robert Baur
Copyright 06.03.2004 by archiv.korallenriff.de
Translation by Peter Scmiedel (Thank you very much )