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pH Probe Conumdrum...


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Hi all!

 

I'm having an issue with my Milwaulkee #SE220 probe that I'm using with a Milwaukee MC122 pH controller.  I use this in my 40G breeder, but I also use the probe to check pH in my other tanks.

 

The 40G is my high tech tank with high LED lights and CO2.  I just use my well water in it which naturally has a GH of 5.5 and a KH of 7.  Mixed community tank with my Bloody Marys....  They love it and thrive...

 

A month or two ago, I set up a new 11 gallon True Aqua rimless for some *georgous* PRLs I got from TropicalAquarist.  I used ADA Amazonia (regular) and cycled it.  I'm using Poland Spring Distilled Water that I get from the grocery store.  I'll probably get my own RO unit in a month or so.  I reconstitute it to a GH of 6 with Salty Shrimp GH+.  I leave the KH at zero.

 

The weird thing is, that my pH probe won't read the pH correctly.  It reads the pH as being somewhere in the mid 7's (it varies).  I didn't believe it, so I broke out an API low pH drop test (not expired).  The API test tells me that the pH is at 6.7, which is what I'd expect from DI water and Amazonia soil....  That seems about right....

 

I called Milwaukee, and they sent me out a new probe.  But the new probe does the same thing....  The probes seem to read everything else correctly...  It reads my well water correctly (which the API test agrees with) and the calibration fluids at 4 and 7.  But it just reads the water in the new tank wacky.

 

Any thoughts?  Has anyone ever had a similar issue using either ADA Amazonia soil or Salty Shrimp GH+?  Or is Poland Spring just evil water?   (LOL)

 

Thought I'd ask around here before calling Milwaukee back.  One thing I'll say for them, they have great support, in that they'll send out replacements at the drop of a pin.  But I'm thinking that maybe they won't know either.....   And a I've already had a replacement...

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How long are you leaving the new probe in the Amazonia tank to stabilize?  It could take some time to settle since I'm assuming your bloody mary tank has a pH of 7-8.

 

Another thought would be electrical interference.  My understanding is that this is rare, but could occur if you have something in the tank or something that runs along the length of your probe wire.

 

Lastly, I would mention that my conversations with American Marine on this topic did arrive around the inherent difficulties in accurate pH measurement in the low TDS, softwater environments that we provide for Caridinas.  I'd have to imagine that with a Milwaukee their probe is able to handle these scenarios, but just a thought.

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Hm I'm having a similar issue with my Hanna handheld pH meter. Tends to read a little on the high side. Next time I'm going to turn off filter and see if that seems to improve accuracy.


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I remove water from the shrimp tank with a clean cup, take it over to the other tank and set it on the edge of the tank stand with the probe in it.  I swirl the probe around a bit.  Leave it in 15 - 20 minutes.  One time I left it in overnight because my CO2 tank was empty (I need to get a back up). 

 

I've noticed that in my well water, it can take 5 - 8 minutes for the probe to find the correct pH.  But with their calibrators it finds the correct pH within seconds.

 

I checked the TDS in the shrimp tank and it's around 165.  My well water runs at about 155 from the tap.  The 40 gallon breeder is at about 175....  So I don't think the TDS is the issue.

 

I do think that whatever they make their calibrators out of is very 'friendly' to their probes.  Because they find the correct pH so quickly as opposed to water.  So maybe it's something in the Salty Shrimp+ that interferes with it?

 

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Huh, I think it's the water...

 

I remembered I had some bottles of water that my sister brought over to me a week or two ago when we had a power failure due to a snow storm.  So I had another sample of someone elses' water in my house...

 

Guess what?  She lives in Poland, Maine.  The same town that the Poland Spring Water they sell in the stores comes from.  (Not sure how popular it is outside of Maine, but every store here sells it).  People love it.  And they make a distilled version of it that they sell in the stores around here in Maine, and that's what I used.

 

My sisters' water is almost as weird!

 

Hers' tested out at a TDS 40, KH 2, GH 0, API pH 6.4.  But the pH was all over the place on the probe.  After 30 minutes the probe measured 7.4, then after an hour it hit 6.6 (better) but now it's headed back up again.

 

So I think it might be the water.

 

I tested the Poland Spring Distilled water, and it came out with a TDS of 0, Kh 0, GH 0 and pH of 6.0 (!) on the API test, but it's bouncing all over the place on the probe.  After about 5 min. it hit 7.0...  but 15 minutes later it was at 6.6 until I swirled the probe in the water which sent it up to 7.2....

 

Today or tomorrow I have to head into town and will pick a few bottles of another brand of DI water and see how the probe reacts to that.

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  • 2 weeks later...

Well, I think it's just an inherent difficulty in the pH probes ability to find a value in reconstituted RO/DI water, like Shrimple Minded said.  The Kmart brand of distilled water acts just as wacky as the Poland Spring brand of DI.  The pH is 6 right out of the jug, but does rise with off gassing.  KH, GH and TDS all = 0.

 

I guess I'll have to rely on the API liquid drop test.  Kind of disappointing, as you'd think the companies who make these probes would tackle the issue and resolve it.  But I guess Aquarists using reconstituted RO/DI are too small a population for them to worry about it...

 

It could be something in the salts that we're using to reconstitue the water.... 

 

But thank you all for the comments.  It puts my mind as ease.  And now I know to just stick with the drop test for an accurate value...

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When I called American Marine and discussed this subject, I left the conversation with full faith that my Pinpoint is giving correct results.  The technical discussion went over my head and was long enough ago that I can't remember the specific details to pass along here.  

 

I had originally inquired because I ordered an HM Digital HM-80 to use as a comparison and on other tanks, but once received I noted drastically different results than from my Pinpoint.  Additionally, I would note that the HM pen could show different results in the same tank during different tests, whereas the Pinpoint gives the SAME result every time.  After my discussion with American Marine I returned the HM-80.

 

I now feel comfortable that if my Pinpoint is dual-point calibrated (pH 4.0 and pH 7.0) that the value displayed is correct.  If I pull the probe out and test in calibration solution right now, it will show pH 4 and pH 7 respectively, and when I return it to the tank, the pH goes back to the same spot.  

 

Lastly I would say that if you want more detail, call the Customer Service line for American Marine, listed on their website.  The two times I've called it was answered by Lou Dell, who I believe either owns or started the company.  He is well informed, well spoken, and interested in hearing about people who use his products.  One of the best customer service interactions I've ever had with a company........twice.  If it sounds like I've drank the kool-aid, it's because I have.

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I use the American marine pinpoint ph probe as well.  I run mine with a reef keeper controller and I get the same results as Shrimple minded posted above.  I went this route because I was having unreliable results from a pen style ph tester and wanted something accurate.  This ph probe was hands down the most referred out of everyone I asked on 3 different forums. 

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This is really great info, thank you Shrimple and Chappy. I am pretty disappointed with my Hanna pen, even though the brand is known for some lab grade equipment. I wonder what differentiates pen vs. probe?


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Yeah, I second the thanks for the reviews.  Think I'll try an AM pinpoint probe. 

 

It irritates me.  I worked in a biotech lab for years...  These instruments are supposed to be accurate, precise and dependable.  To find out that it's common knowledge that there's an issue, and that the manufacture's can't explain it or won't bother looking into it is unacceptable.

 

Think I'm going to make them explain the issue to me and if they can't, I'm asking for a refund and trying a pinpoint.  The Milwaukee probe has a 2 point calibration at 4 and 7.  And it hits the standards dead on.  So why does it work with my well water and not with a solution of DI water and salts?  That's a pretty common thing to do in a laboratory, where they're selling a lot of these probes...  They only way I noticed it was when I tried to compare it to a known sample.  So folks using their probes in a lab environment may or may not be getting the right results.  And lots of important things depend on that.  Like research and pharmaceutical manufacturing....  You just check the standards and assume everything's okay if the standards are reading right.  I can't count the number of times in a lab where I measured the pH of a buffered solution I made...

 

:(

 

Shame on them.

 

 

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Same here , using am pintpoint...

It calibrated corectly and measure wrong.

I just use only api to for the ph . measures.

 

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Same here , using am pintpoint...
It calibrated corectly and measure wrong.
I just use only api to for the ph . measures.
 


So your pinpoint is not working as well as others have experienced? That's disappointing =(


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With probe ph is always very lower than api ph test..

Think that in the past i try 3 diferents am pinpoint probes, not all news.

And the three was calibrated correct, but read diferent ph in the same tank.

Thats why i dont use them, just measure ph with api ph test, and in planted tanks see plants and fish...

An example, in sullawesi water, with mineral 7.5 , probe read ph 6.1.

I dint found why that big diference using liquid ph test and using ph meters, so i just using api ph test for sure.

 

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I use my Milwaukee probe in a planted community tank with my well water.  It's attached to a pH controller (also Milwaukee) and does a great job of keeping the pH at 6.9, which is enough CO2 with my KH to make the plants grow great  while allowing a safety margin for the fish and Neo shrimp.  So I love it for that, and it works great.  And I guess I'll keep it unless I become aware of a probe that will work for both my well water and reconstituted RO/DI.  I'd go with that probe (if it existed) simply because I'd have more confidence in it.

 

But for the shrimp tank with the reconstituted RO/DI, I think I'll have to stick with API.

 

Nicpapa, mine was both lower and higher.  It was just plain all over the place...  But the API test gave me a steady reading, and one that I believe to be true because of the parameters in my shrimp tank.  It's got ADA Amazonia soil which should buffer the pH to about 6.8 with at least a 2" substrate depth.  And that's what the API read.  6.8.  But the Milwaukee probe was giving readings that ranged from 6.0 to 7.6! 

 

Yeah, not very useful...  Will be sticking with API for the shrimp.

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  • 3 weeks later...

I started with the API Master kit but in the mid 7 range it is hard to get discernible results. I eventually ordered an Ohaus from Amazon and it was great for the first 3 months or so but started giving me readings that I did not believe to be true. So then I started confirming with the API. But the Ohaus can't be calibrated ?? I have Tigers, RB, OEBT and now Red all at about 7.4-7.6. 

I had used the Oakton pH pens at a former job with very accurate results for over a year before someone let it dry out! So hopefully that will end up being a better investment with my Golden Bees otw ? I now need to be accurate at lower #'s as well

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Did you use the pen on RO/DI?  Maybe a pen would be accurate...  haven't tried.  I'm just using the API kit on my shrimp tank now.  My sister has a pen and I keep meaning to ask her to bring it over and try it out.....

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Yes I use it on my RO water. DI water can be rougher on the life expectancy of the probe. The familiarity I have with DI water caused me to stay away from it for my aquariums. It is awesome to clean with but wants to absorb anything that gets too close to it. Its like parasite water, sucking the life out of all who touch it ?

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5 hours ago, jessaweeshrimp said:

Yes I use it on my RO water. DI water can be rougher on the life expectancy of the probe. The familiarity I have with DI water caused me to stay away from it for my aquariums. It is awesome to clean with but wants to absorb anything that gets too close to it. Its like parasite water, sucking the life out of all who touch it ?

 

Makes sense.  Funny I never thought of it that way and should have.  If there's nothing in it, then everything that's soluble will dissolve in it until it achieves equilibrium.  It would soak up everything around it like a sponge....

 

I had a pen, but got lazy with it.  I stored it on it's side and the storage solution leaked out and it dried up...  Maybe I should get another and be better about storing it.  They're so cheap nowadays on eBay....

 

Thanks for the input and insight.

 

:)

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No problem and if you have the materials on hand, I believe you can clean it with IPA alcohol with a soft cloth and recondition by soaking for a long while in a storage solution. DI will shorten the life of electrode bulb big time, wayer is okay but Storage solution is best ?

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