# PH Test accuracy



## Hammer (Apr 22, 2010)

I have to normal range PH test from API that shows my water somewhat in the "blue", like 7.4. I have a high range test from Nutrafin that shows it in the orange at 6. Not sure what to believe. This is important because of the type of fish I am hoping to keep and the plant set-up I want. I hoping for high 6's but I am not sure. I know one test uses phenylthalene (sp) as an indicator. Just wondering if anyone had insight. I tend to to see what I want to see when I have I an idea about something.


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## jbyoung00008 (May 16, 2011)

Save yourself the guessing game. Go buy a PH pen from J&L or a hydroponic store. $40 to $60, Its one of the best investments Ive bought especially with more than 1 tank. If you do buy one. Always keep solution in the cap. If the probe dries out it will give wrong readings. You calibrate it with solution so you know its are always accurate.


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## 2wheelsx2 (Apr 21, 2010)

The range will not be accurate at neutral pH's. The 7.4 should be accurate if your kit is not out of date.


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## Hammer (Apr 22, 2010)

Thanks for the thoughts both of you.
jbyoung, what makes the pen so accurate? Is it not based on some similar chemical indicator (just more better??). 

2wheelsx2, are you saying that if I am close to neutral the wide range work be as accurate? (Hooray...I'm close to neutral...I can live with that). I suspect you are right with your thought on the 7.4. I was hoping to be lower. I'm still suspicious about my five year-old DIY Sikaconcrete/stryo backgroun that I really like. I was trying to confirm a suspected 0.2/0.4 buffering effect. I did read that Nutrafin wide range tested low and about a Ph score "out" in some situations.


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## Rockman (May 19, 2013)

Yeah... one of those tests is wrong (could be an expired test kit, or you're just using it wrong). Maybe take a sample to the LFS as a tiebreaker.

But yeah... pH meters are awesome. They're digital; so they use electronic sensors (a glass electrode) rather than chemical indicators. For most purposes a $10 ebay one is workable (although they're not fantastically reliable; you have to calibrate them all the time). Liquid kits are usually accurate within about half a pH unit (the API kit, for example, has .2 unit increments for most of it's range; but it's hard to tell exactly which colour it matches up to on the chart). Digital meters are usually accurate within +/- 0.1 units.


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## 2wheelsx2 (Apr 21, 2010)

Those kits will not be able to measure that accurately that small a difference. The pH pens measure conductivity so will be much more accurate. But unless you pay for lab grade equipment they won't be accurate to much more than say .3 - .4 I believe. The consumer grade just aren't calibrated that accurately. Even with the lab grade probes, when you do that calibration you can see how much they drift (I run 2 American Marine probes, one on my DA controller, another on a pinpoint ph monitor).


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## 2wheelsx2 (Apr 21, 2010)

Rockman said:


> Digital meters are usually accurate within +/- 0.1 units.


My wife works with setups worth thousands of dollars in her lab and she says even those have to be calibrated every week to get to .1 accuracy. She laughs at me repeatedly trying to calibrate my pinpoint meter to .1


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## jbyoung00008 (May 16, 2011)

Ph pen is simple. It comes with ph 7 solution and ph 4. To calibrate it all you do is soak it in ph7 solution than hit calibrate. Than.you place it in ph 4 solution. Hit calibrate. Now its accurate. As long as you calibrate it every week or all is.good. i have a $500 ph meter and it requires the same calibrating. Being off by .2 is still better than your eye tring to figure out if the tester is greeny blue or blue or is it more yellow. "Were not.trying to build a piano here".its quick and easy and a whole lot easier than a test kit that might be expired or not, or is it? Its hard to.see the date lol. Ph pen takes fish tanks to a whole new level. 

Just my 2 centz


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## Rockman (May 19, 2013)

2wheelsx2 said:


> My wife works with setups worth thousands of dollars in her lab and she says even those have to be calibrated every week to get to .1 accuracy. She laughs at me repeatedly trying to calibrate my pinpoint meter to .1


I feel like you're wrong. +/- 0.1 is definitely within the reach of commercial grade probes. A good lab grade pH probe should be able to do down to 0.001.

Drift is another thing. If you're using a handheld probe it's probably a good idea to calibrate before every use (especially for the cheaper ones).


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## Hammer (Apr 22, 2010)

I guess I'm looking at a Ph pen


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## jbyoung00008 (May 16, 2011)

Good choice. You wont regret it. I wish they made pens for gh and kh.


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## Kimrocks (Aug 30, 2011)

jbyoung00008 said:


> Good choice. You wont regret it. I wish they made pens for gh and kh.


Hi Justin - Which brand do you use? There seem to be quite a wide variety on Amazon.Ca

Neewer pH-009 IA Pen Type pH Meter Digital Tester Hydro
by Neewer
CDN$ 18.55

HDE Hydroponic Aquarium Pool & Pond Digital pH Meter Tester Pocket Pen
by HDE
CDN$ 8.25CDN$ 24.99

Dr. Meter PH001 High Accuracy Pocket Size pH Meter with ATC (Automatic Temperature Compensation) Backlit Light...
by Dr.Meter
CDN$ 22.99

Brainytrade - Digital Ph Meter Tester
by HDE
CDN$ 9.35

MOGOI(TM) New Mini Digital Pen Type PH Meter PH-009 I Multimeter Tester Hydro With MOGOI Accessory Wire Winder...
by MOGOI
CDN$ 10.29

SODIAL(R) PH-009 IA Pen Type PH Meter & Digital Tester Hydro New
by SODIAL(R)
CDN$ 10.39

PH Meter Digital Tester Hydro, PH-009 Mini IA 0.0-14.0pH Pen Type
by milliongadgets
CDN$ 11.66


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## Hammer (Apr 22, 2010)

Yeah any suggestions anyone? Good work Kimrocks! I never knew I had so many choices. I heavily leaning towards the Brainytrade because it's 9 bucks


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## Arcteryx (Nov 23, 2011)

Damn. I was going to look to see if things like gh & kh pens exist... I guess not?


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## CRS Fan (Apr 21, 2010)

A TDS meter can be used as a gauge for "hardness", but you'll want to know what's in your water sample first. A TDS meter will pick up all "dissolved solids" within a sample including carbonates, magnesium and potassium salts among other things.

Best regards,

Stuart


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## Chiumanfu (Oct 30, 2014)

Just make sure the one you get has ATC automatic temp correction. pH is variable with temp so the ones with ATC do the math for you.

My other tip is to never let the tip dry out. Use proper storage solution or pH4 calibration buffer in a pinch. If the sensor dries out even just once, it will never be the same unless you have some HCL to recondition it.


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## Hammer (Apr 22, 2010)

Good info. Cheers


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## jbyoung00008 (May 16, 2011)

Here is the 1 I have. I prefer to buy locally. If I have issue with it. I have somewhere local to return it to. I bought mine from BCH green house supply in Langley.


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## Hammer (Apr 22, 2010)

Cheers jbyoung, 
This stuff becomes more relevant when you are get into more fragile species, plants, co2 etc. This is a world I am just dipping more toes into right now.

My understanding of the ph meter is that it uses a supplied solution, that acts a baseline to "calibrate" the device. There are storage and calibrating solutions. The last part being: stick it your tank and read the number. That's what I get so far.


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## jbyoung00008 (May 16, 2011)

Thats exactly how it works. Always clean it under the tap before dipping it in the tank. Rinse it off before storing. Ph falls in fish tanks over time especially in BC due to no KH in our tap water. These pens are the best. Ive had fish for 25 years, A PH pen is heaven sent and would of made life easier in my early fish keeping years  Another great invention is the Magfloat glass cleaner. I dont have a tank without one.


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