Accuracy of test kits?

Discussion in 'Water Chemistry' started by foxfish, 9 Feb 2012.

  1. foxfish

    foxfish Member

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    I have read quite a few post on this forum stating that standard test kits are not to be relied on!

    However it seems that the vast majority of forums still quote their tank parameters based on using commercial, readily available test kits?

    So are they any good or not?

    What can we test for & which ones are not accurate?
     
  2. Tom

    Tom Member

    From testing several NH3 kits against known concentrations in college, we didn't find an accurate off-the-shelf one, with Tetra being the least accurate iirc. Also, if you look at the colour charts - Do any of them actually test down to the supposed lethal levels of NH3 (0.02mg/l), let alone be accurate to those levels?

    Yet by law, shops etc. have to provide evidence of testing, regardless of accuracy.
     
  3. Radik

    Radik Member

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    So which one not off the shelf would you recommend? Same lab. grade one perhaps? Do they exist?
     
  4. dw1305

    dw1305 Expert

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    Hi all,
    NH3 is a really tricky one to test for, even with an ion selective electrode. Same applies to dissolved oxygen. This is partially because they are gases. Nitrate and orthophosphate are possible to test for by colorimetric methods, but other compounds can interfere with the readings. The measurement of pH is slightly different in that you can measure pH with either a meter or indicator strips/titration, but you really need some measure of dKH (temporary hardness) to interpret it. Temporary and permanent hardness you can obtain ball park figures for with a test kit.

    It was because of the difficulties of measurement of these parameters that the BOD (Biochemical Oxygen Demand) techniques were developed. Measurement of total BOD is very time consuming, so people tend to use a combination of 5 day BOD test and a biotic index to estimate water quality. Neither technique is of much use to us, although marine aquarists are using a measurement of Redox potential (oxidation-reduction reactions) which would use the same general idea, but is only relevant for carbonate rich alkaline water and again values would need some interpretation.

    Conductivity you can measure pretty accurately with a £25 dip meter, but you need to have some idea of which solutes (salts and weak acids) are present in your water.

    cheers Darrel
     
  5. foxfish

    foxfish Member

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    Thanks guys but is it not amazing how virtually every fish keeper relies on shop bought test kits! :?
     
  6. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    Not amazing at all. It's the result of a neural interactive software we call The Matrix.
    The Matrix tells you what to think, and you think it. This is exactly why realty often seems more bizarre than fiction.

    Cheers,
     
  7. Ady34

    Ady34 Global Moderator Staff Member

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    Hi,
    this worries me as a fish/plant keeper, it seems more like a neat retailing trick to enhance the sales of water buffers, conditioners and purifiers.
    I was posting on another sub forum, and the hobbyist grade test kit scenario came up. George Farmer alluded to the idea of there limitations.
    I generally use ph, gh and kh test kits to help me with water management in my soft and low alkilinity water area. Im currently buffering to maintain a reasonable GH (4-5dgh ish) for mineral content and some KH (2-4 dkh ish) for reassurance really. Are hobbyist grade test kits able to give results that you can work with for these tests, or are they too a waste of time and money?
    It would be good to find out what if any brands offer the most consistency/accuracy.
    I know more seasoned plant growers can tell from there plants if any deficiencies appear and react to that specific need, however as more of a beginner i like to try and provide some of the basics in the water itself, especially as i buy off the shelf fertiliser (TPN+). Im also presuming, perhaps wrongly, that minerals in water which give you your gh and kh levels are some of the same minerals we provide for our plants with the addition of fertilisers?
    Any help/clarification would be much appreciated.
    Cheerio,
    Ady.
     
  8. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    Hi,
    Can't see why you need to be worried at all. Part of the ingenious programming of The Matrix is a little subroutine that tells people to worry, so they worry for no good reason at all. For example The Matrix tells people to worry about pH fluctuations, so people scurry around spending their whole lives measuring and trying to stabilize pH. The wise entrepreneur invests in the companies that manufacture pH test kits, or in those that manufacture pH controllers. The people who aren't worried about pH (or KH or GH) don't have problems due to fluctuating pH.

    It is a fact that the same elemental components that are responsible for GH also happen to be micronutrients. But there are only two of these; Calcium and Magnesium. Fundamentally therefore, it would be wiser to worry whether or not you have enough Ca and Mg than to worry about GH. If you're using RO or live in a soft water municipal area then simply adding a few teaspoons of Calcium salts and Magnesium salts at water change time solves that problem immediately. Measuring GH actually doesn't tell you anything because GH does not tell you how much Ca or Mg you actually have. GH only tells you what the sum of the two are. Even if you live in a hard water area, you can still add these to see if it makes a difference. Once you confirm whether adding these salts makes a difference or not, you then no longer need to measure GH.

    In the case of these parameters, worrying causes lots more problems than not worrying. If you want to worry then worry about CO2/flow and distribution. That's whats so sad about the whole test kit soap opera. Worrying about test kit readings diverts your attention away from where you really ought to be worried. Ironically, no test kit can tell you much about nutrient/CO2/flow and distribution. You have to look at the plants. I don't see why you need to be seasoned. Can you tell when you have algae? Of course you can. Do you have a lawn? Well, go outside and look at it. Can you tell if the grass is a nice deep dark green, or if it is pale or has a yellow tinge? If so then it's a very similar indication inside the tank. Nutrient test kits never could tell you any of this and that's why everyone continues to have problems, because they think that a test kit can tell you something better than what you own eyes can tell you.

    Since test kits are all basically made the same way, using the same chemistry, how could you possibly hope to determine what brand is more accurate or more consistent? The BRANDS aren't even real. There probably aren't even that many test kit manufacturers in the world. The reagents are probably made in a few places and simply branded or bottled differently depending on the contract. I mean, most pH test kits are Bromothymol Blue. Do people actually think that Company A, or Company B, or even Brand X actually produce their own Bromo Blue in their own labs from scratch? I'm pretty sure they just go to the lowest bidding Bromo supplier, buy the reagent in bulk, chuck it in a bottle and put their label on it. It wouldn't surprise me if they all used the same suppliers. So you could easily have several competing brands whose products are identical inside the bottles. Isn't that just business as usual?

    So at the end of the day, understanding the fundamentals of plant growth and using your eyeballs is much more important, and is much more useful than the information that any hobby grade test kit can give you. But this is not something to be depressed or worried about. It's actually the good news, because your eyeballs were given to you for free. :)

    Cheers,
     
  9. Skatersav

    Skatersav Member

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    I've spent a lot of time trying to distinguish between coral red, cadmium orange and burnt amber. Having concluded that I would need to employ the services of a skilled interior designer to aid me in my weekly testing regimen, I decided that these test kits were truly useless and gave up using them for about 10 years. When I started focusing on keeping plants about a year ago, I was told that I needed to keep nitrates and phosphates at a 10:1 ratio and so would need to start measuring these compounds again - I think there is probably some credible scientific logic behind the 10:1 ratio, but determining whether your tank has this ratio or not using these test kits is not difficult, it's impossible - it simply can't be done. Having spent quite a bit of money on the test kits and quite a bit of time squinting at various hues of orange and light blue, I have given up on them again.

    One thing to think about is the error brackets in a test. For instance, say you buy into the 10:1 ratio thing and are trying to monitor this number. You test for nitrates and determine that it is 10mg/l. Even if you have correctly identified the correct colour you have an error range of at least 7.5 to 15mg/l (half way between the 10mg/l gradation and the next above and below). So, if you do the same thing with your phosphate and determine it to be 1mg/l (rejoice and hallelujah, the ratio is 10:1 and my plants will now explode with luscious growth), but the error range on this is probably something similarly ludicrous: 0.75mg/l to 1.5mg/l. This means that the range of ratios that may exist in the tank is somewhere from 5:1 to 20:1. And that's assuming you haven't squeezed in an extra drip or tipped in a little too much powder with the tiny spoon, and that you have identified the right colour on the chart. Now, one would expect the plants to be able to thrive at a range of n:p ratios but the above testing process still seems pretty futile - how much more enlightened are we having spent the time and the money?

    I have reverted to my previous view on these test kits (slightly embarrassed that I was duped into spending time and money on it again having had very few problems with my fish for ten years in spite of not testing), and have given up testing again. I simply do a big water change once a week and follow a fert regimen.
     
  10. Ady34

    Ady34 Global Moderator Staff Member

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    Hi there,
    i hear you on this one and sometimes it just needs putting into word context for people like myself who had previously been fishkeepers, and naive ones at that, to see it for what it is. I had relied upon test kits for 10 years or more whilst keeping fish and continually struggled with 'guesstimate' results based on colour renditions. The margins for error involved are clearly too large to rely upon results for anything more than a vague idea!

    your right, but im one of those programmed to believe in it and it takes time to accept after its all youve known. Since starting my first planted scape ive had my eyes opened to several 'myths' of fishkeeping for example PH fluctuations being unacceptable, when clearly the addition of C02 for the planted aquarium shifts ph on a daily basis with no ill affects, something im sure that happens in nature after rainfalls etc.

    Well that certainly clarifies that question, and i suppose to some degree i was coming to that conclusion myself from various research and problems ive experienced. Ive just last week began dosing sera mineral salt to add Mg, Ca and K as a possible remedy for a continual crypt melt issue, and hey presto (maybe too early to say for sure) the plants are much stronger for it.

    Again this is useful to know as both salts can be added in the required dosage to ensure enough of both rather than a shortfall of one or the other. Its not rocket science when you know, and seeing it in black and white helps me to understand better.

    Advice duplicated by others including Geroge Farmer on another thread..... about time i changed my thinking!

    Agreed to a point, however I can see when i have issues, its just diagnosing the deficiency which isnt as straightforward until you have some greater experience and understanding of what it is your looking at. For example, I may think i have a potassium deficiency because i have holes in my leaves, but i dont know for sure yet as i havnt personally experienced adding K and seeing the plant thrive.

    oops, not finished, ive come back to edit this sentence on as i hit the 'submit' button by accident, there is a more polite ending on the next page.
     
  11. Ady34

    Ady34 Global Moderator Staff Member

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    OOPS... wasnt finished and pressed submit by accident,

    Im beginning to understand this, as i have said in the last post its just a little difficult to get all you have known out of your head and relearn. Only from being a part of an organistaion such as UKAPS, and asking the questions can we learn more. Having Global Moderators, and experts who are willing to spend their time posting replies is a privilege we have here on UKAPS and every bit of advice is something new learned!!.... and its often less expensive too!!
    Thanks,
    Ady.
     
  12. foxfish

    foxfish Member

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    Thanks for the answers & discussion.
    I wonder how this debate would fair on a more fished based forum like PFK, no doubt many thousands of folk rely on test kits as part of the hobby!
     
  13. Ady34

    Ady34 Global Moderator Staff Member

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    Indeed, i was one of them who relied upon them like gospel. They have a place but as is becoming apparent to me, only as a very general guide. I think in future for me, test kits will be used only during 'cycling' routines to check highs and lows of ammonia, nitrite and nitrate readings. They may not be entirely accurate but when following the same procedures, they can show changes to 'zero' levels of ammonia and nitrate for example which shows trends rather than specifics to help ascertain safe perameters for the introduction of livestock.
    Other than that my eyes will tell me the rest. :thumbup:
    Cheers.
    Ady.
     
  14. George Farmer

    George Farmer Founder Staff Member

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    When discussing test kits I think it’s important to differentiate between ‘general’ fishkeepers and planted aquarium owners.

    In a non-planted tank there’s little or no nutrient export except via water changes and/or chemical adsorption. Perhaps there’s de-nitrification in some circumstances.

    For this reason in a non-planted tank it may be more prudent to rely on test kits to measure things like NO3 and pH regularly. These are a good indicator if your maintenance regime is effectively dealing with the waste build-up. The same with PO4 kits.

    Although kits themselves may be inaccurate they still have their use in these types of aquariums for spotting trends.

    Actual ppm (mg/l) levels aside, it’s fair to say that a NO3 test kits results will show the fishkeeper whether their nitrate levels are on the up or not if they test regularly using the same kit. If the NO3 does increase over the weeks then it’s time to change more water, give the substrate a better clean, or maintain the filter more frequently.

    The same principle can be applied to a drop in pH, which is commonly associated with excess organic build-up. High nitrates and low pH are classic symptoms of “old-tank syndrome” and test kits are a good indicator to help identify this.

    KH and GH test kits are also a good indicator of roughly how hard your water is so you know whether it’s appropriate to keep Rift Valley cichlids or wild-caught discus (although a TDS or conductivity meter may be more appropriate).

    Obviously most modern planted aquariums are fundamentally different and the consequent nutrient management through plants growth, nutrient dosing, and water changes renders testing almost redundant, except for pH and hardness when choosing appropriate livestock.

    I also advocate the use of KH3/4 and NO3 kits when stocking for the first time after using new Aqua Soil-style substrate.

    In summary test kits have their place but IMO shouldn't be relied upon in a planted tank to determine exact parameters. They can be useful to perform basic trend analysis and to determine baseline parameters for tap water.
     
  15. dw1305

    dw1305 Expert

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    Hi all,
    I'd agree with that, they should give you a ball-park figure. From my experience on other forums the one that people have most trouble with is actually pH, particularly now that a lot of soft tap water is being treated with NaOH to raise its pH above pH7. Once you are into the realms of buffering and adding carbonates to water where the "pH is already too high" you begin to encounter (or possibly engender) real confusion.

    cheers Darrel
     
  16. sWozzAres

    sWozzAres Member

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  17. Crispino Ramos

    Crispino Ramos Newly Registered

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    Home test kits may not be 100 % accurate but they can give you a rough estimate. Combining that with planted tank observation, the amount of maintenance you have done - you can do something to solve a problem. :idea:
     
  18. dw1305

    dw1305 Expert

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    Hi all,
    Looks interesting, a little colorimeter. These work by shining a beam of light, (set to a certain wave-length) through the solution in the cuvette (little perspex box with 2 clear sides) over a known distance of light path, and then measuring the % light aborbance (or transmission) at the wavelength that corresponds to the colour that the reagent and sample compound create.

    The greater the amount of light being intercepted by the sample the larger amount of your test substance in the water.

    This isn't usually a linear relationship, it is a curve, but by diluting your sample you should be able to get it onto the initial linear section of the standard curve.

    I'll do phosphorus, as that is a test you would often use colorimetry for, even in a lab situation. You would need to know which reagent it uses, in this case it looks like it is the "ascorbic acid/ammonium molybdate" method. http://www.advancedaquarist.com/2011/8/review>
    from <http://water.epa.gov/type/rsl/monitoring/vms56.cfm>.

    I can see a couple of problems straight away, you can't create a standard curve, unless you use at least 3 of the "starter pack of 6 reagents for Phosphate", and have access to a phosphate standard solution so you would be reliant on the internal standard curve used as a datum by the colorimeter, also potassium antimony tartrate is a poison, so won't be in the reagent, or if it is this would make it impossible to make up your own reagents, and you would be reliant on buying the Hanna ones.

    Having said that the results in the "Advanced Aquarist" review look pretty good. This is the comparison with a Hach spectrophotometer costing several thousand dollars.
    [​IMG]

    Would I buy these? personally I wouldn't, but they should be slightly more accurate than using colour strips for orthophosphate or nitrite, but you would still have the problems of interpretation etc.

    My suspicion would be that they will sell, but only in limited numbers to Reef Keepers etc.

    cheers Darrel
     
  19. foxfish

    foxfish Member

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    Hmmm there seems to differing opinions here!

    So the kits are not accurate but, use them all the same so you can obtain a ball park figure.

    Once you have a ball park figure, if you keep using the same make of test kit, then you should be able to see a change :?

    I am still confused :crazy: my main concern is for the thousands of folk who not only rely on test kits (matrix effect) but insist upon there use..... I mean look at any fish keeping forum (including this one) & you will see hundreds of post empathising just how important it is to test your tank water & your tap water.

    I think it would take a brave man to stand up on a reef tank forum or any large fish keeping forum (PFK) & start a thread titled "test kits are not accurate"

    There does seem to be all the evidence to prove that statement but I guesse there are not that many people who want to admit to something that they have been preaching for years.

    Look at all the books & magazines articles that quote ideal water chemistry & what you need to achieve to keep plants or fish, which one of those authors is going to admit that by writing "you should test you water", has in fact been giving out a near impossible challenge ?
     
  20. ceg4048

    ceg4048 Expert/Global Moderator Staff Member

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    It doesn't take someone brave, just someone who understands the truth. As discussed on several other threads about test kits the problem runs deep because there are several fallacies of logic at play. The first being the belief that the kit is accurate and the second being that people are told to fear certain parameter values when they actually don't need to. So if you are prepared to attack test kit accuracy, then you also have to attack the fear of that parameter.

    How difficult has it been for Tom Barr to convince people that nutrients don't cause algae? How about that the addition of inorganic Nitrate salts is not dangerous to livestock? A very difficult proposal. So if someone has a fear of NO3 because they think NO3 causes algae, and that NO3 is responsible for poor livestock health you are going to have trouble convincing them that not only are the test kit readings false, but that the readings are irrelevant even if they were accurate, because the problems in the tank are not related to this particular parameter.

    It's the same story for pH and KH. People panic when they find out that a certain substrate affects the KH and pH in the tank. Shockingly, it actually affects their sediment choice, and they run away from an otherwise excellent product just because it has an effect on a parameter that doesn't even matter. My reaction is always; So what? Why should I care what the pH and KH does after sediment addition? Neither plants nor fish will care, so why should I? So really, test kits and their bogus readings are not the root cause of the problem. Irrational fear of the very same disciplines of chemistry that nobody wanted to learn when they were in high school is the culprit. People think they will find solace in those little colored vials because they don't want to trouble themselves with the more difficult task of learning the truth. The test kit is only the tip of an iceberg that runs deep in our psyche.

    Cheers,
     

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