# PH accuracy?



## kilnakorr (24 Jun 2020)

I got a new PH monitor today. I kept the old one in the tank, but calibrated both.

They both measured the same PH in the tank, but once CO2 started  they didn't drop at same rate.
Currently I have 6.4 and 6.7 readings?!

I tried doing a test with buffer and they are both accurate.

What could the difference be? Could there be this much difference in each side of the tank?


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## hypnogogia (24 Jun 2020)

Yes, there probably could. For a valid comparison you should place them side in the tank.


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## Zeus. (24 Jun 2020)

kilnakorr said:


> but calibrated both.



Yes, been there both probes correct at 4.0pH and 7.0pH with buffer yet vary in between when in the tank. With pH being on logarithmic scale and probes being very sensitive and made to different specs I think this is inevitable.

But on the other hand do with need an accurate measurement of pH for our tanks? what advantage does knowing the actual pH  yield? IMO/IMO *none.*

I don't even bother calibrating my probes anymore. The DC gives the approximate [CO2] and the probe tells me if its stable. If you have two probes in tank and one reads  6.4 and the other reads 6.7 form lights on till CO2 off +/-0.1pH what does it matter both are relatively stable so [CO2] stable. There is no magic pH level


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## kilnakorr (25 Jun 2020)

Zeus. said:


> But on the other hand do with need an accurate measurement of pH for our tanks? what advantage does knowing the actual pH yield? IMO/IMO *none*


You are right, and I don't really care about the specific PH. But when tuning in CO2, I'd like to know if the probes are reading right. They both measure same value in tankwater, but with CO2 injected they don't drop at same rate.

I'm starting to think, I have a PH goblin in the house messing up my readings...

PH of degassed tank water: 8.3
PH tank water in tank : 7.5
PH with CO2 (yesterday): 6.4

Looks like a 1.9 drop, so currently I really have no clue what PH to aim for


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## Zeus. (25 Jun 2020)

kilnakorr said:


> PH of degassed tank water: 8.3
> PH tank water in tank : 7.5
> PH with CO2 (yesterday): 6.4



Looks like my figures  



kilnakorr said:


> Looks like a 1.9 drop, so currently I really have no clue what PH to aim for



Use the DC colour change. Once the pH is stable wait 2hrs from when pH did not change and the DC colour is the approximate [CO2] . If fish floating in tank your too high , fish swimming at surface or pass out when feeding - your close to limit. Snails all at top off tank - too high


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## kilnakorr (25 Jun 2020)

Zeus. said:


> If fish floating in tank your too high , fish swimming at surface or pass out when feeding - your close to limit. Snails all at top off tank - too high


I had 2 fish at surface yesterday, and a bright yellow DC, so might be a little to much.

Currently, doing a new profile and will aim / tune  for 6.6

I also, recalibrated both PH readers again, so hoping they'll agree on the PH drop


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## Zeus. (25 Jun 2020)

When I use two probes (which I normally do) the reading never match


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## kilnakorr (25 Jun 2020)

Zeus. said:


> When I use two probes (which I normally do) the reading never match


So far so good. 6.8 and 6.81


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## kilnakorr (25 Jun 2020)

Zeus. said:


> When I use two probes (which I normally do) the reading never match


Are you using two probes as a fail safe? Just be sure the readings are still reliable?


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## Zeus. (25 Jun 2020)

Just to check there is no drift in the probe when I'm doing the profile, so just a double check. Last time I did it they was a difference of 0.4pH on the different probes


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## kilnakorr (25 Jun 2020)

Zeus. said:


> Just to check there is no drift in the probe when I'm doing the profile, so just a double check. Last time I did it they was a difference of 0.4pH on the different probes


Makes sense.
Update: I now got 6.6 and 6.67 (6.6 and 6.64 when lights on 3 hrs ago).
I adjusted midway, as I could tell bps was to low to get there in time for lights on.
DC is lime green, and all fish are active showing no signs of stress.
Gonna do a new profile tomorrow, and hopefully my K2SO4 arrives tomorrow for a new batch of ferts.


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## Zeus. (25 Jun 2020)

kilnakorr said:


> I adjusted midway, as I could tell bps was to low to get there in time for lights on.



Was you pH stable before you adjusted ( I assume you mean you adjusted the BPS/injection rate) if it was adjust it back and just shorten the CO2 on time before lights on.

Adjusting the BPS/injection rate will change the time it takes to get the pH drop but also changes the target pH and stable pH. Reach your target pH/[CO2] , get it stable and the drop time is the drop time ( unless you have duel injection/solenoids/timers)


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## kilnakorr (25 Jun 2020)

Zeus. said:


> Was you pH stable before you adjusted ( I assume you mean you adjusted the BPS/injection rate) if it was adjust it back and just shorten the CO2 on time before lights on.


Yes, it was pretty stable at around 6.8, or at least dropping VERY slowly.
Just checked and have 6.6 and 6.67, so been amazingly stable, for the last few hours.
Just need to see how long this takes, and maybe just add a little more, as it looks like I can push it a little more


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## jaypeecee (25 Jun 2020)

Hi @kilnacorr


kilnakorr said:


> I got a new PH monitor today. I kept the old one in the tank, but calibrated both.



Sounds like you have good quality pH probes/electrodes/monitors. Which ones are you using?

JPC


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## kilnakorr (25 Jun 2020)

jaypeecee said:


> Sounds like you have good quality pH probes/electrodes/monitors. Which ones are you using?


Yes and no.
My 'old' one is a milwaukee, with a €200 price tag.
Because of a facebook discussion, I came across a cheap chinese 6 in 1 measuring device for €65. Had to try it. So far so good, but if it will last more than 2 months is the question


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## jaypeecee (25 Jun 2020)

Hi @kilnakorr 

Thanks for the info. It will be interesting to see how the cheaper model behaves over time.

JPC


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## kilnakorr (25 Jun 2020)

@jaypeecee  It will. It has temp, TDS/EC and PH/ORP probes, so plenty of gadgets.
I accidently ordered another one, so I guess I can have both PH TDS and ORP EC running all at once


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## jaypeecee (25 Jun 2020)

Hi @kilnakorr


kilnakorr said:


> I accidently ordered another one, so I guess I can have both PH TDS and ORP EC running all at once



I'm running some experiments with ORP at the moment. It's a tricky parameter to get your head around but I'm making progress with it this time.

JPC


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## kilnakorr (26 Jun 2020)

jaypeecee said:


> It's a tricky parameter to get your head around


I guess it will tell you if something starts slipoing in the tank. I guess we just want a good reading 300-400 and see it stable like many other things in the tank. If it starts to drop, something isn't right


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## jaypeecee (26 Jun 2020)

Hi @kilnacorr


kilnakorr said:


> I guess we just want a good reading 300-400 and see it stable like many other things in the tank.



Speaking from my own experience, those figures (+300 to +400mV) are not easy to achieve. I suspect there are many tanks out there that fall short of this range. All it takes is a small amount of organic waste to drag these figures down towards the +200mV mark.

JPC


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## kilnakorr (26 Jun 2020)

jaypeecee said:


> Speaking from my own experience, those figures (+300 to +400mV) are not easy to achieve. I suspect there are many tanks out there that fall short of this range. All it takes is a small amount of organic waste to drag these figures down towards the +200mV mark.


I actually don't have a clue.
I tested mine for fun, and got 300+. How accurate that is or how the numbers are just before waterchange, is unknown.
Once I get my CO2 dialed in, I can switch probes and do a profile. Just for fun


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## jaypeecee (26 Jun 2020)

Hi @kilnakorr 


kilnakorr said:


> I tested mine for fun, and got 300+. How accurate that is or how the numbers are just before waterchange, is unknown. Once I get my CO2 dialed in, I can switch probes and do a profile.



Yes, that would be interesting. Perhaps you could also check your tap water?

JPC


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## kilnakorr (26 Jun 2020)

jaypeecee said:


> Perhaps


I sure can. Looking for something specific?


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## jaypeecee (26 Jun 2020)

Hi @kilnakorr 


kilnakorr said:


> I sure can. Looking for something specific?



I seem to recall that the Danish water companies don't resort to the use of either chlorine or chloramine as used in some other countries such as the UK. I think the Danish water companies use UV-C sterilization but I may have got my facts wrong. The ORP value of tap water can apparently be anywhere in the range from +220 to +380mV.

JPC


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## kilnakorr (26 Jun 2020)

jaypeecee said:


> I seem to recall that the Danish water companies don't resort to the use of either chlorine or chloramine as used in some other countries such as the UK.


True. It was completely stopped in 2009.
I'll let you know, when I'll have the opportunity to test it. Need some calibration buffer first. Probably not ecpensive, but damn postage is😕


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## dw1305 (27 Jun 2020)

Hi all, 





kilnakorr said:


> I guess we just want a good reading 300-400 and see it stable like many other things in the tank.





jaypeecee said:


> Speaking from my own experience, those figures (+300 to +400mV) are not easy to achieve.


I agree with @jaypeecee. The other issue is that high ORP isn't an unalloyed good thing in a freshwater aquarium. 

There is more discussion in <"REDOX why don't we measure it?"> and <"Canford Park">.

cheers Darrel


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## dw1305 (28 Jun 2020)

Hi all, 





dw1305 said:


> The other issue is that high ORP isn't an unalloyed good thing in a freshwater aquarium.


Following discussion of Carl Stromeyer in <"another ORP thread">, I've just read his <"Aquarium Redox Balance">, which is a good read. 

cheers Darrel


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## kilnakorr (28 Jun 2020)

dw1305 said:


> Following discussion of Carl Stromeyer in <"another ORP thread">, I've just read his <"Aquarium Redox Balance">, which is a good read.


Thanks alot for the links. Interesting read indeed.
Seems ORP is of use. Like most other parameters in the tank, you can use it for stability check and not for chasing a specific value.


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## milesm (1 Jul 2020)

kilnakorr said:


> You are right, and I don't really care about the specific PH. But when tuning in CO2, I'd like to know if the probes are reading right. They both measure same value in tankwater, but with CO2 injected they don't drop at same rate.
> 
> I'm starting to think, I have a PH goblin in the house messing up my readings...
> 
> ...


you aren't off gassing co2 enough overnight. consider installing a surface skimmer or increase surface agitation.


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## jaypeecee (1 Jul 2020)

Hi @kilnakorr


kilnakorr said:


> ...Seems ORP is of use. Like most other parameters in the tank, you can use it for stability check and not for chasing a specific value.



I have been conducting ORP measurements on my experiment(al) tank for a few weeks now and it's proving to be very interesting. I have dabbled with ORP measurements on other tanks over the last few years. In fact, I've discussed the topic of ORP with Carl Strohmeyer on his forum. This time around, I'm determined to decide if ORP is a worthwhile parameter to measure in freshwater tanks. At the moment, I _think_ it may be a good indicator of the overall health of a tank. But, I want to do a whole lot more measurements before I take that final (!) decision. I have accumulated many scientific papers on this topic. I've got to the stage where I don't currently keep many fish, shrimps, snails and plants. But, I'm still an aquarist - I keep water in my tanks!! And I will be resurrecting my main tank as soon as I can safely go out and get a good few barrels of RO+DI water.

JPC


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## kilnakorr (1 Jul 2020)

milesm said:


> you aren't off gassing co2 enough overnight. consider installing a surface skimmer or increase surface agitation.


Already have a skimmer and lots of surface agitation. Even with 48 hrs of no CO2 injection, the result is the same.
Question is not about the starting PH, but 2 probes with different drop values.


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## kilnakorr (1 Jul 2020)

jaypeecee said:


> In fact, I've discussed the topic of ORP with Carl Strohmeyer on his forum.


Link please


jaypeecee said:


> I have accumulated many scientific papers on this topic.


Sharing the info?

I read one of his articles / studies and it's very interesting.
Getting my second monitor tomorrow, and calibration solution friday, so I can start testing

Seems ORP itself is fine, but along with PH even better to get what Carl Strohmeyer refers to as rH value.
Interesting topic indeed


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## sparkyweasel (2 Jul 2020)

kilnakorr said:


> Question is not about the starting PH, but 2 probes with different drop values.


Apparently, pH probes can be susceptible to electrical interference, so that might be an issue. There's some discussion of it here;
https://www.ukaps.org/forum/threads/rise-and-fall-of-ph.40312/#post-437554


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## kilnakorr (2 Jul 2020)

sparkyweasel said:


> Apparently, pH probes can be susceptible to electrical interference, so that might be an issue.


Very interesting. Makes a lot of sense. I'm simply going to take alot of readings and watch the lifestock, while tuning.
Both probes seems to give stable readings throughout the day, so I'm quite sure there isn't any major interference.


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