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Water report vs test results.

Nick potts

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According to my water report my water is soft (13 mg/l Ca, 33ppm, 2GH), but when testing myself I am getting a GH of 12 and a DKH of over 16.

Is it likely the water report results or the home test could be that far out from each other? Or anything that could cause such a rise?

Cheers
 

alto

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User error is hardly an issue with the test kit technology ;)

Investigating Salifert Water Test Kits for Accuracy – Lab Results
October 29, 2017 By ReefHacks

We said goodbye to our samples and mailed them off to ATI Lab in Germany for the advanced ICP-OES water test. The results of this test will offer a clear picture of whether or not these kits are as accurate as some think.

Results

  • ATI Lab Carbonate hardness: 8.85 °dKH
  • ATI Lab Calcium 467.7 mg/l
  • ATI Lab Magnesium 1358 mg/l
  • ATI Lab Nitrate 5.69 mg/l
  • ATI Lab Phosphate 15.76 µg/l
  • Salifert Alkalinity: 8.9 °dKH
  • Salifert Calcium: 460 mg/l
  • Salifert Magnesium: 1350 mg/l
  • Salifert Nitrate: 5.0 mg/l
  • Hanna Phosphorus ULR : 15 µg/


I’d suggest confirming your aquarium results with a local shop and online water report with your water supplier
 

alto

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Or anything that could cause such a rise?
Did you test tap water?
Did you test tank water?
Did you do 50% water change and then retest aquarium water?

Depending on your kit manufacturer, they may have a list of possible interfering compounds (note that most interfering compounds have to be in such high values that your livestock or plants would likely be showing issues)
 

Nick potts

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What about Test Kits ?

I would trust the water report, as that was done in a lab, some Home test kits are not very good, plus can be very user sensitive as well

I understand hobby grade kits are not the best, but there is a rather large difference in the 2 and the test kits can't be that bad surely?

Did you test tap water?
Did you test tank water?
Did you do 50% water change and then retest aquarium water?

Depending on your kit manufacturer, they may have a list of possible interfering compounds (note that most interfering compounds have to be in such high values that your livestock or plants would likely be showing issues)

The test kit is just a cheap API one ( i don't usually test my water), tested both tap and aquarium water, both near enough the same results for gh/kh. Haven't retested after a WC yet.

Plants and livestock appear fine
 

JoshP12

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Hi @Nick potts,

What is the pH and TDS? These readings can be rather meaningless, however, you can use them to see if you are in the ballpark or not - knowing a couple of things.

If plants and livestock appear fine, then I may just keep moving along. Likely your local store will use the same water - you could ask them. like @alto suggested.

The test kits that you are using are based on a titration and can't be 16 dKH error bad.


Josh
 

Nick potts

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Hi @Nick potts,

What is the pH and TDS? These readings can be rather meaningless, however, you can use them to see if you are in the ballpark or not - knowing a couple of things.

If plants and livestock appear fine, then I may just keep moving along. Likely your local store will use the same water - you could ask them. like @alto suggested.

The test kits that you are using are based on a titration and can't be 16 dKH error bad.


Josh

Hi Josh.

My PH runs at around 8ish (6.5ish in tanks with active substrates) and I don't test TDS.

The only reason for the recent testing is i have been picking up more and more shrimp and i know they can be a little more sensitive.

I think i will pick a different test kit tomorrow, i have always used salifert for my saltwater tanks so will try that.
 

rebel

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i have always used salifert for my saltwater tanks so will try that.
Assuming test kits haven't expired, would be really cool to see comparison between api and salifert.

Investigating Salifert Water Test Kits for Accuracy – Lab Results

  • ATI Lab Carbonate hardness: 8.85 °dKH
  • ATI Lab Calcium 467.7 mg/l
  • ATI Lab Magnesium 1358 mg/l
  • ATI Lab Nitrate 5.69 mg/l
  • ATI Lab Phosphate 15.76 µg/l
  • Salifert Alkalinity: 8.9 °dKH
  • Salifert Calcium: 460 mg/l
  • Salifert Magnesium: 1350 mg/l
  • Salifert Nitrate: 5.0 mg/l
  • Hanna Phosphorus ULR : 15 µg/

October 29, 2017 By ReefHacks
These results are very encouraging!! Was this salt water or fresh? I am particularly impressed with nitrate result.
 

Nick potts

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Assuming test kits haven't expired, would be really cool to see comparison between api and salifert.

Test kit is brand new and i agree, however it appears salifert don't do gh or kh for freshwater, at least not in the UK :(

I'll see what my LFS has in stock.
 

dw1305

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Hi all,
According to my water report my water is soft (13 mg/l Ca, 33ppm, 2GH), but when testing myself I am getting a GH of 12 and a DKH of over 16.
Do you know what the conductivity value on the water company report is (min., mean and max. would be really useful)?

cheers Darrel
 

dw1305

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Hi all,
Full report can be seen here.
It doesn't give you the conductivity, but the calcium value tells you have less than 1 dGH/dKH. Derivation for the different units is in the <"Krib link">.

The high pH is because of the addition of sodium hydroxide (NaOH), this might effect the dKH test (it actually measures alkalinity and NaOH is a strong base) but it shouldn't effect the dGH test (Na+ is strongly alkaline, but it doesn't contribute to the dGH, which is the multivalent cations (Ca++ etc)) my guess is that it does because the test kit isn't really measuring the dGH, it is measuring alkalinity and using a conversion factor.

I would like to throw all these kits as far as they would go, until <"the manufacturers"> are <"actually honest about what their kits are measuring">, and their limitations.

cheers Darrel
 

Nick potts

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Just an update.

Purchased new test kits for GH and KH, these are reading 3GH and 3KH for straight tap water, and 4GH and 3 KH for tank, this is much closer to the water report.

It is rather disconcerting that a brand new kit would have such an off result and I wonder how many people might not double-check and take action based on the first results.

Think i will go back to blissful ignorance and not test at all :)
 

dw1305

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Hi all,
Think i will go back to blissful ignorance and not test at all
I'd rather have no test result than an inaccurate one, that is why I like conductivity measurement there isn't much that can go wrong, and it doesn't require any interpretation. The downside is that it isn't the most useful measurement.

Before I started down the <"Duckweed Index"> route, I had expected to be able to recommend kits and meters that would work across the whole range of freshwater types. I knew <"what you could do in an analytical lab">., but I rapidly began to realise that a lot of people (on forums) were reporting results that definitely weren't accurate and probably weren't even in the <"right ball park">.

cheers Darrel
 

alto

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It is rather disconcerting that a brand new kit would have such an off result and I wonder how many people might not double-check and take action based on the first results.
I would definitely contact API and the retailer (who should refund all costs) with this result - and a strongly worded complaint!

API as the manufacturer is who I would target, as they carry the responsibility for Quality Control and can easily label kits with manufacture and expiry dates, also “markers” like that indicate if kit was exposed to vey high temperature (re shipping/storage)
 
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