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pH test inaccuracy


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Just an FYI - I have been testing my pH using the API kit, and my water has consistently been 7.4 to 7.6.

 

I just calibrated my lab pH meter and tested my tank water, and it is 6.85. Not even close to the API test results.

 

Now, I have RCS shrimps who probably couldn't care less about this difference, but for those of you with more sensitive shrimps, this is probably worth noting, especially if you are investing in products to raise or lower your pH.

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My API pH low range test was completely wrong too. A pH meter is really a worth while investment. A cheap eBay one will do fine just make sure it has at least a 2 point calibration and ATC. Take care of the probe tip with proper storage solution and even the cheap ones will last a long time.

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hi sarah thanks for bringing this to my attention! much appreciated :-)

 

i am always getting a result of 7.4 -7.6 in most of my tanks which is the upper end of the pH test kit and lower end of the high range pH test kit. the testkits certainly aren't that wonderful but i've been using them because they come as part of the API master kit and i'm too lazy to maintain my electronic pH tester! i've got one of these but I will definitely need to calibrate it and start using it again when i get my hands on these beauties in a few weeks time!

 

http://www.shrimpspot.com/index.php?/topic/3782-caridina-zebra-new-shrimp-found/

 

love n peace

 

will

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  • 3 weeks later...

I've gone a bit in circles on this one myself.  I had read where the API liquid tests weren't the most consistent, so then I thought I'd pick up an electronic tester since I wanted better accuracy.  So, I got one of the more basic models for around $20 or so, calibrated it, and tested my water.  I watched as the values would keep changing on the electronic tester, and took a while to settle.  I read the detailed directions (I'm a guy, I'll admit after calibrating it, I thought it was just test and go without bothering to read) and what I discovered is that it can take up to 10 minutes for a stable reading.  Now, I was used to 3 drops, shake and read.  To wait 10 minutes with a roomful of tanks to test was not going to be a good long term solution.  After using my tester for a while, what I found was that while the API test didn't match the electronic tester, it wasn't that far off either (like maybe .1 to .2).  I continued to use the tester for a little while longer to satisfy my investment and then just finally stored it away as it wasn't worth the effort in my setup.  Since that time, I've come to realize for the shrimp that I am keeping, my GH, temp and regular water changes are more important than the exact value my pH is at.  I do still check pH if a tank doesn't seem happy, but it's not my first test that I go to.

 

OK, now with all that being said, funny story from just the other week that happened to me.  I have a tank that has ADA AS in it, and I've had it set up for close to 2 years.  I was curious if my buffering was still hanging in there.  So, I grabbed a test tube to do the liquid test, and I noticed it had just a slight haze to it - almost like fine dust.  I looked it over, didn't think too much about it, and did my test.  My test showed into the blue (i.e., over 7.0).  Wow, I thought, it has run out of buffering.  Then I thought, I'm going to test with a couple other tubes.  I tested 3 more times with 3 other tubes (that had no haze) and all were right at that 6.4 to 6.5 range - which is fine for my crystals that I keep in that tank.  So, what I realized was that the first tube that had the high reading wasn't cleaned properly, and that haze was some bit of residue from a poor cleaning job on my part.  I'm sure it seems obvious, but make sure those test tubes are clean.  It doesn't take much to affect those results.

 

Anyway, by no means disagreeing with what other folks are discussing here, just sharing that for the shrimp that I am keeping, the pH isn't the most important parameter that I monitor.  I'd also say that if you want fast reading results, you'll need to get up into the more expensive meters - based on what I have read and experienced personally.  It's been a year plus now, so maybe there are better options at a lower price than when I played in this area.  And finally, one humorous thought that I saw for the first time the other day that might apply here:  a man with one watch always knows what time it is; a man with two watches is never quite sure.

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I agree & use API PH tests; not a electronic PH meter........

I look at testing as protecting my investment bottom line...  So, for example my fancy tiger tanks...  I do 3 separate API PH tests in order to make sure I have the right reading due to the amount of time & energy involved w/these awesome shrimp.  Likewise, this doesn't really take up much of my time testing or cleaning the test tubes in order to protect my investment.  In any case, this is a demanding hobby that requires one's time, patience & the ability/drive to self educate during the unfortunate shrimper learning curves..   Once these hurdles are crossed, your reward will be your 1st berried female but it takes a lot of time & $$$.....

 

Updated:  "unfortunate shrimper learning curves" can be understood as "shrimp woes" or also known as "shrimping ain't easy".....

I use API tests as well for testing PH, but I also get inconsistent results sometimes when I do 2-3 tests in a row. Do you get consistent results? I sometimes draw water from different parts of the tank.

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  • 1 month later...

I asked my sister who is a scientist, she deals with ph testers every day.  While most of what she recommended was way up there in price (thousand or more) this little number is somewhat affordable.  $73. https://us.vwr.com/store/catalog/product.jsp?catalog_number=10065-860. The important thing is that it's a VWR.  Other brand name with a scientific reputation is "Mettler".  She cautioned buying used, as the probe and electrodes would most likely be messed up.  New you can be careful to maintain it properly.  She said with a VWR or Mettler, she would rarely worry about calibration (three months or so), and would usually only do so to confirm that it hadn't gone out of spec.  I would recommend calibrating with solution you buy from Amazon such as http://www.amazon.com/gp/product/B004HE7W42?psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00 $14. often enough until you are comfortable relying on it for longer lengths of time.

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When I follow the link for the $73 meter, it seems to go to a page that doesn't exist on the site.  Would you mine double-checking the link?  I'd love to read more about the meter that she referenced.

 

Thanks!

Chad

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Found it.  It's the Pocket Pro pH Tester by Hatch.  Go to https://us.vwr.com/store/ and search for "Pocket Pro pH, Hatch"  They also have multimeters (pH, TDS, Conductivity in one) for a bit more on VWR's site.

 

You can get it on Amazon and other places. 

 

What I think I like is that it can tell you when it needs to be calibrated.

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I won't recommend pocket type.

 

as when the life of probe ends, you have to toss the whole thing away.

 

Buy standard pH meter with BNC connector type probe.

you can find lots of good probe at very affordable price.

 

probe is only good for a year. no matter how you maintain it.

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I have try 4  different ph controllers, the controllers works fine, but the problems is on the probe.

The probe in a good use, you can measure  correct  ~ for a year.

Keep in mind that probe can calibrate correct and measure wrong... :)

 

Both of three probes calibrate correct at 4-7 ph .

What is the correct? :P

I test and a ph meter from ebay , a yellow one , and read 6.8.

Wiht a api and sera liquid ph meter measure  diferetns ...

 

ba7468c067a44b0bcd5bd40562799d1b_zpsrfqy

 

078127ef2c0c5dbff44bd688cdc07716_zps1qbc

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Did you do a two point calibration on those, or just one?  Also this pen type has a replaceable electrode: https://us.vwr.com/store/catalog/product.jsp?catalog_number=74730-030

 

It's not common and more expensive.

 

BNC probe is the way to go.

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 I'm interested in your BNC probe suggestion James.  Could you tell us what you use?

 

I have Digital Aquatics ReefKeeper Elite and Digital Aquatics Lifeguard.

and I have Pinpoint pH meter also.

 

it all has BNC connector for pH probe. so I can exchange my pH probe on all my meters.

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Do you keep the pinpoint in the tank continuously?  I'm reading that it doesn't hold calibration very well if it's being used as a "dipper" But works well if left in the fluid.  Thoughts?  I'm looking for something with which I can spot test multiple tanks as well as water for my hydroponic garden.

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Do you keep the pinpoint in the tank continuously?  I'm reading that it doesn't hold calibration very well if it's being used as a "dipper" But works well if left in the fluid.  Thoughts?  I'm looking for something with which I can spot test multiple tanks as well as water for my hydroponic garden.

 

Yes, I keep it in the tank all the time.

 

I clean the probe every 3 months, and re-charge the in 100% KCL solution overnight.

then do calibration before use.

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Hi James,

Can you give detail explanation on how to re-charge in 100% KCL solution?

Thanks

 

There are two chambers of the pH probe.

 

Filled with 3M KCl solution.

 

the reference chamber has reference joint connected to the tank water, over time, the K+ ion will escape from the reference chamber, and the probe would become very slow and less accurate.

 

so to do the re-charging.

Basically recharging the reference chamber with saturated KCl solution. to refresh the reference chamber vs the reference joint. 

More K+ ion would go into the reference chamber to restore the proper level.

 

after the treatment, you should see improved the response time.

 

To make 100% KCl solution is simple.

Add KCl (you can find it at Home Depot and Lowes as water softener salt, not cheap NCl, more expensive KCl) to RO water until it can't dissolve any more.

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There are two chambers of the pH probe.

 

Filled with 3M KCl solution.

 

the reference chamber has reference joint connected to the tank water, over time, the K+ ion will escape from the reference chamber, and the probe would become very slow and less accurate.

 

so to do the re-charging.

Basically recharging the reference chamber with saturated KCl solution. to refresh the reference chamber vs the reference joint. 

More K+ ion would go into the reference chamber to restore the proper level.

 

after the treatment, you should see improved the response time.

 

To make 100% KCl solution is simple.

Add KCl (you can find it at Home Depot and Lowes as water softener salt, not cheap NCl, more expensive KCl) to RO water until it can't dissolve any more.

 

 

Thanks James,

Do you dip the probe into the 100% KCL soluation for overnight?

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Thanks James,

Do you dip the probe into the 100% KCL soluation for overnight?

 

Yes, you can keep it in there longer. it's fine.

 

In that case, you 3M KCl solution.

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