# Which NO3 Testing Kit is best??



## REDSTEVEO (12 Sep 2016)

All,

Please don't jump all over me for posting this ,or report me to Clive Ha Ha because I know as advocates of the perfect planted tank we add Macro and Micro Nutrients to help our plants grow. I once tested my NO3 Levels and the coulour changed to a deep dark Merlot Wine colour But the fish and the plants were all fine, so hey ho. So in the past I have not been too fussed about NO3 Levels as I was regularly adding it to my planted tank as part of the EI Fertilser Dosing Technique. 

However now with the 9 x Wild Discus which I am told by the experts are less tolerant to Nitrates I am testing more often before and after water changes. I have heard of some Wild Discus fish keepers changing 50% water on a daily basis, which is not a route i want to be going down. 

When I have tested for NO3 in the past I have always used the Tetra NO3 Testing Kit, 3 x Liquids and 1 x Powder additive. I have tried using different testing kits but find if you compare the results between testing kits you get very different readings so it is hard to know which one to rely on.

Also I have found less and less places sell the Tetra NO3 kits so I finish up having to order them online which is a PITHA.

If you are using NO3 testing kits which ones are you using? By the way I don't like the 3 in 1 or 6 in 1 testing strips so lets not go there.

Cheers,

Steve


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## DanielC03 (12 Sep 2016)

For a year I have made changes to 70% water daily in my planted discus fattening.
The problem is that at that age need plenty of food for everyone to eat necessarily have to give them too much.
Medi never NO3 simply that existing in the market test are not reliable especially for those who add other salts.

That age and size have their animals?


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## AverageWhiteBloke (12 Sep 2016)

I'll get in and out quick before Clive spots this thread  I think you may have answered your own questions Steve especially when you mention that two different tests give two different results. It's admirable that if there's any chance that your Discus may be sensitive to nitrate that you don't want to take it but I suppose you have to ask yourself if you can't rely on what the test is telling you then how further forward are you by testing.

A better way may be to do what I'm intending doing. I haven't added any live stock to my tank yet other than RCS and I'm currently dosing salts dissolved in water at EI levels. Things are going fine at the moment although the biomass will probably increase creating a bit more demand. Once I start adding fish and feeding them I think it's fair to assume that based on my lighting shouldn't burn off all the ferts present and the feeding and fish will generate more no3/po4/co2 that I could safely lower the amount of salts being dosed. I have pre-mixed my ferts so that I add 20ml every other day, using a syringe it means I can reduce very gradually say a ml per month if not longer and see if this has a negative effect on the plants. I'm only intending keeping the potassium sulphate at the same levels as I am now.

Maybe you could find the sweet spot between fish and plants rather than convincing yourself with confirmation Bias and a test kit. Problem with tests as unreliable as no3 tests you could quite easily compound an issue that didn't need to be there in the first place.


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## alto (12 Sep 2016)

REDSTEVEO said:


> By the way I don't like the 3 in 1 or 6 in 1 testing strips so lets not go there


how can I resist 
Buy a pack of the Tetra 6in1 test strips (or if you can track down Machery Nagel under their own label, even better - they do outstanding "strip" technology)
Use pinsettes/twezzers to remove each test strip so you don't contaminate stock with finger oils etc (present even on newly washed hands)
Handling just by the edges, use a sharp, fine bladed scissor to cut strip in half - this way you test tank & tap water with the same strip - pay attention to the technique of using the test strips (I think it's gone over in the directions & help video so won't repeat here)
This is a very quick way to confirm similar parameters on tank/tap water, &  as same strip is used, it removes any chance of slightly different chemistries that may be present between strips

I've used Seachem kits
Nitrate/Nitrite Multitest  


> Includes reference for test validation


choose a kit that does this, in general any brand that is including a positive test standard has also taken care with their kit chemistries.
Salifert, Hach, Seachem have always been on the more reputable team, you may find other brands equally good, look for companies that produce water testing kits for the scientific market & then have an aquarium line as a side product, or an aquarium trade brand that is having their kits manufactured by a science market company

(if you've read my soapbox oratories, I think kit testing can be precise & accurate within the needs of aquarium chemistry - the main factor is human error - though there are some garbage kits out there.
 (when I ran my own test of 5 different brands, only one was consistently "off" ... I was working in a research lab at the time so pretty simple to do ))





REDSTEVEO said:


> I have heard of some Wild Discus fish keepers changing 50% water on a daily basis, which is not a route i want to be going down.


This is a time proven method to successfully keeping wild fish ... there are many compounds that accumulate in aquarium water beside the obviously measureable, daily water change is the best method of assuring water quality ...
I'd be doing 25% daily water changes on your Wilds, after 4-6 weeks, you might move to alternate day 25% water changes or twice weekly 50% water change
Much depends on how you intend to feed these fish - anything beefheart & you need to do a water change after every feeding (in addition to scheduled water changes)

(again my soapbox oratory   read Sverting's comment  re feeding discus on Seriously Fish species profile - this is based upon published journal articles with discus stomach content analyses .... cant remember if I've linked this before for you  )

If you're doing the water changes, there's no need for nitrate kits - or worry on the accuracy of the reading 

I keep mostly wild fish, I do 75% water changes every 3 days (I keep soft water fish as that's what my tap is, so I can just use the Python water change system) even in lightly stocked tanks.
Pristine water is the best disease preventative you can offer fish, water quality also impacts behaviour


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## REDSTEVEO (12 Sep 2016)

I have tested the water for NO3 four times today, before and after the water change using two different test kits, one from Tetra and one from Waterlife. Before the water change the Tetra kit was a slight yellow tinge giving a reading of 5 ppm, after the water change virtually the exact same reading, so the water change made no difference. The Waterlife test kit showed zero ppm before and after the water change, so very confusing not to mention frustrating.

So far I have got the wild discus eating Tetra XL Flake food, Tetra Prima, Piscine Mysis Shrimp, Freeze Dried Californian Blackworm, and Freeze Dried Black Mosquito Larvae. I have only fed them on small amounts of BH as a supplementary and hope to wean them of it if possible as long as the weight and size stays healthy.

Oops sorry have to go Tea is ready. Will post more later.

Cheers,,

Steve


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## AverageWhiteBloke (12 Sep 2016)

REDSTEVEO said:


> I have tested the water for NO3 four times today, before and after the water change using two different test kits, one from Tetra and one from Waterlife. Before the water change the Tetra kit was a slight yellow tinge giving a reading of 5 ppm, after the water change virtually the exact same reading, so the water change made no difference.



Apologies if I'm stating the obvious but could there be no3 in the tap water?


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## REDSTEVEO (12 Sep 2016)

Every time I have tested my tap water no matter what test kit I used there is according to the test results, absolutely zero NO3 present. I live in Wales and the tap water is of excellent quality, soft, low KH and GH PH around 6 to 7 and a TDS of 130.

Steve


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## AverageWhiteBloke (12 Sep 2016)

Now you can see why Clive gets so frustrated with them  A lot of the problem is the perception of colour. Depends on what mood you're in on what the reading is.


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## REDSTEVEO (12 Sep 2016)

Picking up from where I left off earlier. I forgot to mention in addition to all the other foods I am feeding my Discus I am also feeding them Live White Worm, so as varied a diet as possible.

Back on the subject of NO3, I think we sometimes underestimate the ability of fish to adapt and acclimatise to varying conditions over time. Take for instance Discus in the wild, they go through seasonal changes of heat and temperatures, low and high water levels, plentiful to scarce food supply and varying water conditions. What happens between the dry season and the rainy season, after being in low water in the dry season the water will be warmer, the concentration of waste products increasing, changes in water chemistry etc. 

Then come the floods sweeping soil, mud, forest debris, animal faeces, and all kinds of land based detritus, which I am sure must play havoc with the water chemistry. But...and here is the key, as long as these conditions are not permanent the fish will tolerate these changes and adapt. 

I am making some large assumptions here, but I agree with something Clive has always said when people have brought up the topic of testing kits, ( we all know he disagrees with them) but he advocates look for the signs, are the plants looking healthy, growing well with no algae problems, are the fish swimming about, not breathing heavily, feeding well and showing no signs of stress, then surely all is well with the water conditions. 

My contradiction lies not with NO3 and plant health, but in what the experienced wild discus keepers are telling me, big water changes and as often as possible. I am going for two water changes per week using a mix of RO and HMA filtered water at around 30 to 40 percent and monitor the progress of the fish. I may have to change this if there are adverse signs, but I know for a fact that when I go on holiday for two weeks, my neighbour who feeds my fish while I am away will not be changing the water four times a week.

Cheers,

Steve


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## AverageWhiteBloke (12 Sep 2016)

For sure the fish and plants will be the first to let you know when something is amiss. Its quite a hard thing to do is giving up on test kits, we are dealing with a transparent liquid which in the main is odourless as well. Sometimes we just want some reassurance that everything is ok, I don't think we'll get that from test kits unless we are prepared to spend major money and considering a water change is probably the best way of solving any issues and a fraction of the price makes you wonder if testing certain things is worth the hassle at all.
I guess sometimes having no information is marginally better than having wrong information.


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## rebel (12 Sep 2016)

You could use TDS as a surrogate marker to trigger a water change. Set a tds that is acceptable to the wild fish. If you are very keen you could calibrate your test kit and your tds to get a more consistent reading.


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## REDSTEVEO (12 Sep 2016)

I have done some crazy things based on the paranoia from the results of test kits. Like staying up all night mixing kettles and pots full of boiling water with tap water in an attempt to virtually refill a tank after almost 100% water change in a few hours.

Someone once said on this forum, 'The only things that happen quickly are usually bad things'

Steve


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## dw1305 (13 Sep 2016)

Hi all,





REDSTEVEO said:


> Every time I have tested my tap water no matter what test kit I used there is according to the test results, absolutely zero NO3 present.


You can get figures from your water company, it will give you a minimum, maximum and mean value. If your water comes from mid-Wales it may be very low in nitrates, even in the S. of England you can get low nitrate water in certain circumstances (our water comes from a deep limestone aquifer and is low in nitrates). 





REDSTEVEO said:


> but he advocates look for the signs, are the plants looking healthy, growing well with no algae problems, are the fish swimming about, not breathing heavily, feeding well and showing no signs of stress, then surely all is well with the water conditions.


I think so, the difference is that you can maintain much better water quality in a planted tank, compared to an non-planted one. 

For whatever reason I think a lot of cichlid keepers tend to see plants as a _take it or leave it_ tank decoration, rather than the most important component in biological filtration.  

I don't see any reason why you can't use a combination of the Duckweed Index and a TDS meter. Have a look at the <"High nitrate"> thread for details.

cheers Darrel


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## ian_m (13 Sep 2016)

There are NO3 test kits that are relatively immune to interference by other ions present. Known interfering ions with hobby test kits are chloride (present as a reaction from chlorinated water) and also most dechlorinators, even in trace amounts. These test kits have reagents that remove the chloride (silver sulphate ?) and other interfering ions before testing the nitrate.

Test kits like this will give reasonably reliable readings of nitrtae and use of colour wheel means colour misinterpretation is reduced.
http://uk.hach.com/nitrate-test-kit-model-ni-11/product?id=26427780260&callback=pf


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## dw1305 (13 Sep 2016)

Hi all, 





ian_m said:


> These test kits have reagents that remove the chloride (silver sulphate ?) and other interfering ions before testing the nitrate.


It is the "Zinc reduction method" that eliminates interference from Cl- ions, the principle is the same for all the tests, NO3- is reduced to NO2-, and this is measured by colorimetry. The cadmium reduction method is more accurate, but you have the cadmium issue. 

All nitrate compounds are soluble, but some nitrites are insoluble meaning that you can use them for colorimetry. I'll work on the theory that your water isn't going to have any NO2, so the intensity of the red azo dye (or yellow ("amber") colour) is a measure of NO3, (rather than NO3 and NO2).

You can tell which test a kit uses by the colour you measure, red is azo dye, and cadmium reduction gives an amber colour. 





ian_m said:


> Test kits like this will give reasonably reliable readings of nitrate and use of colour wheel means colour misinterpretation is reduced.
> http://uk.hach.com/nitrate-test-kit-model-ni-11/product?id=26427780260&callback=pf


 I would probably use the Hach type test kit if I was obliged to use a test kit (this works via cadmium reduction). 

cheers Darrel


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## REDSTEVEO (13 Sep 2016)

http://uk.hach.com/nitrate-test-kit-model-ni-11/product?id=26427780260&callback=pf

Just looked at this testing kit, it's priced at £99.00

But on reflection a bog standard NO3 testing kit from Tetra or API, JBL etc etc cost around a tenner a go and give you between 30 and 50 not necessarily accurate test results, so may be worth it if the results are more dependable.

Will Investigate further.


Thanks everyone for their contributions,

Steve


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## ian_m (13 Sep 2016)

REDSTEVEO said:


> Just looked at this testing kit, it's priced at £99.00


Well you did ask "Which NO3 Testing Kit is best??" and now you have your answer. Even recommended by Darrel that he would use this test kit. Nitrate test done.


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## dw1305 (13 Sep 2016)

Hi all,





ian_m said:


> Even recommended by Darrel that he would use this test kit.


I would, but even then I wouldn't really be confident about the result. 

We use "Ion Selective Electrodes"  in the lab. for student work, but they require a certain amount of care in use. 





REDSTEVEO said:


> Just looked at this testing kit, it's priced at £99.00


 Ion Selective Electrode kit would start at about £1000 for an electrode and analyser, the electrodes have a limited life and are ~£150. 

You would still need to make up NO3 standards and construct a calibration curve etc. 

If you wanted to get accurate and repeatable results (like a water company would need), you are probably now looking at HPLC <"High Performance Liquid Chromatography">.

cheers Darrel


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## REDSTEVEO (13 Sep 2016)

Looked again at the Hach Website, it says it will do 100 tests. So at £99.00 that works out at just under £1.00 per test, I.e. 99 pence. The measurement range is up to 40 mg/l. Does that mean if your water has more than 40 mg/l you can't tell how much?

If I tested my NO3 six times per week, once before and after each water change the kit would last me for about 16 weeks so roughly three and a half months. 

I will have to look at the cost of refills to see if this worth the expense.

Thanks Ian and Darrell for you much appreciated technical expertise and advice.

Steve


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## REDSTEVEO (13 Sep 2016)

Just spoke with one of the tech bods at Hach Laboratories in Manchester. The replacement Reagents for another 100 tests costs £29.70. so once the initial test kit has been bought, the subsequent tests with the replacement Reagents would only cost around 3 pence per test.

I asked some other questions about testing water with a higher reading of 40mg/l. From here it got slightly complicated but here are the facts according to my notes.

1. N is only a fraction of an NO3 Molecule.
2. If the result of the test reads 5mg/l as N, you multiply the result by 62 and then divide by 14 to express the result as NO3.
3. So 5mg/l x 62 divided by 14 = 22mg/l NO3.

Slightly confused by this next bit and not 100% confident I understood completely but here goes.
If the reading was 75mg/l (i.e. higher than the 40 range of the kit) you dilute the test solution with de-ionised water at a rate of 1 to 1 - 50% test solution and 50% de-ionised water which results in a measurement of 37.5 x 2

I don't want to confuse anyone so please don't take this literally until someone who knows exactly what they are talking about responds.

The bottom line is if your water is under the 40mg/l of the test kit you will be fine and each test will initially cost 99 pence per test, but once you have bought the replacement reagents the cost drops to 3 pence per test.

Well worth considering if we can get our head around the maths equations.

Ian, Darrell??

Thanks,

Steve


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## kadoxu (13 Sep 2016)

REDSTEVEO said:


> Slightly confused by this next bit and not 100% confident I understood completely but here goes.
> If the reading was 75mg/l (i.e. higher than the 40 range of the kit) you dilute the test solution with de-ionised water at a rate of 1 to 1 - 50% test solution and 50% de-ionised water which results in a measurement of 37.5 x 2



It does makes sense... but you start by saying the end result, which makes it more confusing.

So you have 5ml of water reading something above 40mg/l.
You add 5ml of de-ionized water, meaning you now have the same amount of NO3 in twice the water volume (10ml).
If you can read something bellow 40mg/l, let's say 25mg/l, in 10ml of water, it means you originally had 50mg/l of NO3 (=25x2) in 5ml of water.

If, on the other hand you still read 40mg/l, you have to repeat the process, adjusting the math.


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## dw1305 (13 Sep 2016)

Hi all, 





REDSTEVEO said:


> If the result of the test reads 5mg/l as N, you multiply the result by 62 and then divide by 14 to express the result as NO3.


 When the test measures in elemental nitrogen (N) it will give you a much smaller number than if it measures NO3.

The RAM of N = 14, and O = 16. In NO3 you have a RMM of 14 + (3*16) = 14 + 48 = 62. So this where the "14" and "62" come from.

So NO3 is 14/62 ~ 22.6% N.

If you divide your 5 ppm N by 0.226, it gives you 22.14 ppm NO3.

You don't really need the maths, if you multiply the N value by 4.5 you are pretty near the NO3 value (22.5 ppm). 





REDSTEVEO said:


> If the reading was 75mg/l (i.e. higher than the 40 range of the kit) you dilute the test solution with de-ionised water at a rate of 1 to 1 - 50% test solution and 50% de-ionised water which results in a measurement of 37.5 x 2


When you have a sample that reads above your highest standard (in this case you don't have to create a calibration curve, Hach have already done it), you need to dilute that sample so that the value lies on your calibration curve. Because you've doubled the sample volume with DI water (which doesn't contain any NO3) you need to double the recorded value (37.5 * 2 = 75)

Curve is actually a bit of a misnomer, because ideally you want to read the sample value near the origin of the curve, in the initial linear section.

This is one of the problems, if you did as suggested your value (right at the top of the curve) would probably still be an underestimate of the true NO3 value. You can carry on dividing your sample by 2 with DI water (1:2,1:4 (multiply value by 4),1:8 (multiply by 8)) until you get a repeatable value, but in the case of _off the scale nitrogen_ a 1:10 dilution (1 part tank water, 9 parts DI water) would be more likely to give a more accurate result.

The question really has to be is this process likely to give a better estimation of NO3 values than visual estimation of nitrate provided by the "Duckweed Index" and a conductivity reading? For me the answer is probably not.

I get quite a few PM's on other forums that start with a statement like, 





> I know I don't have any nitrate because my test kit says so, but I have to take out handfuls of Duckweed every week, what is happening?


and I tell them to trust the plants.

cheers Darrel


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## REDSTEVEO (13 Sep 2016)

So err...this Duckweed Index...just chuck a bunch of Duckweed in the top of the tank, if it turns yellow, then low levels of NO3, if it stays dark green and spreads like wildfire, then NO3 levels too high right...

Just read other articles re 'High Nitrate Levels' and saw the difference between Organic and Inorganic NO3. The stuff we add as part of EI is Inorganic, so not harmful, or at least not as much as Organic caused by poor filtration, over feeding, overstocking and poor water maintenance.

What type of Duckweed are we talking about here?


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## dw1305 (14 Sep 2016)

Hi all,





REDSTEVEO said:


> So err...this Duckweed Index...just chuck a bunch of Duckweed in the top of the tank, if it turns yellow, then low levels of NO3, if it stays dark green and spreads like wildfire, then NO3 levels too high right..


<"Yes">. It doesn't sound as accurate as looking at changing colours on a test kits, but really it is the same approach, but just much more robust. 





dw1305 said:


> If your plant grows quickly, and is dark green, you have lots of nitrate. They use this approach for <"crop plants">


The _<"Lemna_ bioassay"> is widely used in waste water treatment, and <"phytoremediation"> with floating plants is used to clean up all sorts of polluted wastes. The problems with _Lemna_ were that it doesn't like very soft water,  it needs reasonably high levels of nutrients and it is a PITA to harvest. After some experimentation I found that there was a "Duckweed" that didn't have these limitations, and it was Amazon Frogbit _(Limnobium laevigatum).  





Chris Jackson said:



			The Optimum Aquarium (Horst and Kipper)
		
Click to expand...

 _I subsequently bought a copy of <"The Optimum Aquarium">, to find that the authors had used a similar approach to the Duckweed Index in the 1980's.   

Because plants needs about x10 the amount of nitrogen (N) and potassium (K) compared to phosphorus (P), (and x3 times more phosphorus than any of the other elements) deficiencies are most likely to be nitrogen or potassium. Other options that cause chlorosis are magnesium (in older leaves) and iron (in younger leaves). Nitrogen and potassium deficiencies show up in old foliage first, and both cause yellowing (chlorosis) and smaller leaves. 

Floating plants aren't CO2 limited and show a really quick greening, and growth response, to added nitrogen. If you add nitrogen, and your plants green, they were nitrogen deficient, if your plants are a large, lush dark green they have plenty of nitrogen. When you harvest a plant you remove nitrogen (largely incorporated into the photosynthetic proteins) from the tank.   

cheers Darrel


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## dw1305 (14 Sep 2016)

Hi all, 





REDSTEVEO said:


> The stuff we add as part of EI is Inorganic, so not harmful, or at least not as much as Organic caused by poor filtration, over feeding, overstocking and poor water maintenance.


Pretty much, usually in aquariums (and eutrophic rivers etc.) nitrate is the final product from the oxidation of ammonia, the NO3 itself isn't toxic until you reach significant levels. Fixed nitrogen (nitrogen that organisms can utilise) is a scarce resource, so in nearly all natural situations it never accumulates, so when you have a lot of it it is a marker of pollution.

In non-planted aquariums high levels of NO3 indicate that you aren't doing enough water changes, because NO3 is only removed by anaerobic denitrification and/or water changes. 

Planted aquariums are different, because the plants directly take up both NH3 and NO3, and are net oxygen producers. High levels of dissolved oxygen mean more efficient biological filtration and efficient biological filters are "nitrate factories". 

We need to add nitrogen to heavily planted tanks because nitrate levels fall over time, rather than rising. If we don't add any nitrate, plant growth will slow as nitrate levels fall. I still have water changes, but I only change a small volume of water ~10% ~every day.

I keep _Apistogramma, _which come from similar water conditions to Discus, and I use a combination of Duckweed Index feeding and conductivity measurement for tank management. 

cheers Darrel


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## Paulwilsonwhite (5 Jan 2020)

Hi.
I find this information very helpful and another way of keeping your tank healthy.
I will just digest what I’ve read and put together some questions because this is truly interesting 
Cheers Paul


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