What about Test Kits ?

ian_m

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Many people ask "What test kit should I use to test my tank water ?" or "My test kit says my nitrate is high ?", so before posting a question on test kits and hobby test kit results, please read the quoted text below from ceg4048's excellent article on "The Estimative Index (EI) Dosing with Dry Salts".

"The Estimative Index (EI) Dosing with Dry Salts".
https://www.ukaps.org/index.php?page=dosing-with-dry-salts



What about Test Kits?

I can think of three things I really dislike about keeping aquariums. The first is cleaning/removing algae, the second is water changes and the third has got to be testing. Normally, when a beginner walks into pet shop to buy his/her first tank, one of the first things the attendant will push is a test kit. Test kits are often included in a package deal. We therefore grow to associate teats kits as a normal part of aquarium husbandry so many are shocked when I advise to bin the kits. I’ll explain here my reasons for rejecting testing:

1. Hobby grade test kits, for our purposes are inaccurate. That would not be so bad in and of itself but they are also inconsistently inaccurate. This means that one day they can be merely marginally wrong and the next day the same kit can be grossly inaccurate. A simple change in humidity can throw off a kit’s response.

2. Test kits are expensive. The more accurate the kit the more expensive. Hach produces some of the more reputable test kits but they may be ten times as expensive as the basic kit.

3. The test kit, even the more accurate ones may not tell you anything that you don’t already know if you are following the dosing scheme. If you dose 7ppm nitrate this morning and your tank uses a maximum of 3ppm, then by the end of the day you know that you have at least 4ppm remaining. In the EI dosing philosophy you only care about having at least some target value in the tank. The objective is to avoid falling below the uptake rate limit. If you have more than this limit then great, but because you know how much you dosed you then know absolutely that you have at least that much.

4. The type of algae that develops in our tanks normally occur for specific reasons and due to specific nutrient deficiencies. The appearance of a certain type of algae therefore tells you what you what nutrient requires more dosing.

EI therefore does not require testing because a known amount of nutrients are added to the tank thereby eliminating any ambiguity. Of course if you enjoy testing then by all means test, but just be aware of the pitfalls.
 

jaypeecee

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Hobby grade test kits, for our purposes are inaccurate.

Please be aware that this is a very generalized statement. I am satisfied that some test kits are trustworthy. My background is in the physical sciences and I use test kits. Absolute accuracy is not necessarily all-important. We're not running a water company. Sometimes, we are just looking for trends. Is ammonia on its way down? Is KH getting perilously low? If in doubt, ask!

JPC :)
 

hypnogogia

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Out of interest, what Nitrate test do you use, and what do you suggest is an acceptable upper limit? I see really mixed reports on keeping nitrates below 10ppm, and others that talk about 20-30 for decent plant growth. It’s very confusing.
 

jaypeecee

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Out of interest, what Nitrate test do you use, and what do you suggest is an acceptable upper limit? I see really mixed reports on keeping nitrates below 10ppm, and others that talk about 20-30 for decent plant growth. It’s very confusing.

Hi @hypnogogia

I use a combination of the JBL Nitrate liquid test kit and the ITS Nitrate/Nitrite test strips. You may not have heard of the company, ITS. It's an abbreviation for Industrial Test Systems. Here's their European website:

https://www.itseurope.co.uk

Please note that, being a US-based company, nitrate is quoted as NO3-N and this needs to be multiplied by 4.4 to convert it to UK units.

As for an acceptable upper limit, I don't know if any reliable figures are available for ornamental fish. But, figures are available from open waters - rivers and streams. It's not ideal, is it? But, it's either that or just guessing as far as I can see. Figures are available for both acute toxicity and chronic toxicity. The latter is generally of more interest to me. Now, because I'm having problems with my computer, I'll just provide a link to a useful NZ website:

https://www.ecan.govt.nz/data/document-library/

The document of interest is Report No. R09/57 'A review of nitrate toxicity to freshwater aquatic species'.

Hope that helps.

JPC
 

dw1305

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Hi all,
I see really mixed reports on keeping nitrates below 10ppm, and others that talk about 20-30 for decent plant growth. It’s very confusing.
It is because of the way that we arrive at any given nitrate (NO3-) level.

Aquascapers add nitrate as the NO3- ion, usually via potassium nitrate (KNO3), but in all in other circumstances the NO3- ions are the end product of nitrification, the microbial oxidation of ammonia (NH3). People are really using the level of NO3 as <"a proxy for the earlier higher levels of toxic ammonia and nitrite"> or as an <"agricultural pollution indicator">.

The scientific literature <"has some of the same issues">.
I am satisfied that some test kits are trustworthy.
I'd be happier with some rather than others, you should be able to get <"relatively accurate values for orthophosphate"> (PO4---) with a <"low range kit">, but there are a number of issues with testing for nitrate, mainly because it doesn't form any insoluble coloured compounds.

Nitrate test kits work by reducing the NO3- to nitrite NO2- and then <"combining that nitrite to create a further compound that is "> coloured. There still isn't any intrinsic reason <"why you shouldn't be accurate"> if you follow the scientific method, but now there are quite a lot of <"single points of failure">.

cheers Darrel
 

jaypeecee

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Hi Darrel,


Of course, we don't need to use a proxy when we can directly measure ammonia and nitrite. Such test kits are readily available and many aquarists use them.

I'd be happier with some rather than others, you should be able to get <"relatively accurate values for orthophosphate"> (PO4---) with a <"low range kit">, but there are a number of issues with testing for nitrate, mainly because it doesn't form any insoluble coloured compounds.

FWIW, I use the JBL Phosphate kit and it serves me well.

Nitrate test kits work by reducing the NO3- to nitrite NO2- and then <"combining that nitrite to create a further compound that is "> coloured. There still isn't any intrinsic reason <"why you shouldn't be accurate"> if you follow the scientific method, but now there are quite a lot of <"single points of failure">.

Here, I use the JBL Nitrate kit. Just follow the instructions and all will be well. But, try to do the colour matching with natural daylight. I am aware of the 'single points of failure'. In fact, it was possibly me that sent you the paper to which you are referring. I would also add that some nitrite and nitrate test kits report results as NO2-N and NO3-N, respectively. In such cases, the appropriate multiplication factors will be shown on the container.

JPC
 

dw1305

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Hi all,
Of course, we don't need to use a proxy when we can directly measure ammonia and nitrite.
That is sort of the point, we do need a proxy.

It is not so much the measurement, although I would say that ammonia /ammonium measurement is not entirely unproblematic, it is more the toxicity of these compounds and their transitory nature. Often nitrate is the "smoking gun" left over from an earlier pollution incident, it is marker and we know stoichiometrically that one molecule of ammonia is converted to one molecule of nitrate. The residual nitrate can only be removed by:
  1. Dilution (water changes, either natural or in the aquarium).
  2. Uptake by plants
  3. Anaerobic denitrification.
If we don't have these processes the NO3 just remains in solution.

The analogy I would use is measuring ammonia and nitrite is like going outside and measuring rainfall by standing outside for an hour everyday and collecting the falling rain. You might carry out the procedure following the scientific method, but you may not record any rain, even if you are in the eye of a hurricane. Measuring the rainfall ("nitrate") using a <"tipping bucket rain gauge"> would be a much better method, but even that would only give you snap-shot, until you had a long period of measurement.

cheers Darrel
 

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