# PH monitor suggestions - continual use



## Andrew Butler (15 Nov 2019)

I'm wondering if anyone knows of a tested device they use for continually monitoring the PH levels in their aquariums? I've a half decent Hanna pen already but should have the space to hide a probe and have the display in cupboard which would allow me to keep a rough eye on things easier. I'm not looking to spend crazy money but likewise don't want one that's either an absolute load of rubbish or I need a lottery win to purchase.
I've found a few while looking though but nothing is jumping out at me, I realise it will quite possibly not just be PH Any suggestions welcome.


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## ian_m (15 Nov 2019)

I do have some knowledge in this area and to measure pH properly in a live system is hard and expensive. This is why there are not many "hobby grade" pH meters in use in fish tanks.

To do it properly, as industry does, you need a "big boy" pH probe eg
https://www.omega.co.uk/pptst/PHE-4580.html
Should be fine. You will need to add isolation valves so it can be removed, cleaned and calibrated regularly.

You will also need a meter to read pH value, this will do.
https://www.omega.co.uk/pptst/PHCN37.html

You will also need a temperature sensor, as all pH probes have temperature dependence, though with a fish tank it is liable to be constant temperature. Something like this will be fine, again needs to be removable for cleaning.
https://www.omega.co.uk/pptst/M12TX-PT100.html

So easily done for £500 or less.

pH measurement is hard, the voltage levels are tiny in mV levels. The slightest dodgy wiring or electrical leakage from your pumps/lights/filter etc and the reading becomes meaningless.

In the end why do you want to measure pH. You get a value of 6.3, so what, what are you going to do about it. Nice value to know but not exactly useful.

pH measurement might be useful to set CO2 levels, but you require a differential value ie pH before CO2, pH after CO2, not an absolute value.

I have never properly measured my waters pH (OK test strips once or twice), it is something I do not need to know or anything I can change the value of or anything that would make change something.

I just ensure my drop checker is green/yellow, fish are happy and plants grow cm daily, thus all is OK.


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## dw1305 (15 Nov 2019)

Hi all, 





Andrew Butler said:


> I'm not looking to spend crazy money but likewise don't want one that's either an absolute load of rubbish or I need a lottery win to purchase.


You need a solid state ISFET probe, if you are going to use it in the tank long term. You also need an ISFET probe where it uses a "reference field effect transistor" (REFET), rather than a silver chloride (AgCl) glass reference electrode.

Even with the tanks in the lab. I very rarely test the pH and I definitely wouldn't rely on a pH probe to adjust the CO2.

The problem with pH is that is isn't a simple parameter to measure, or interpret, and pH meters are complicated <"high maintenance bits of kit">. 

I'm not a CO2 user, but if I was I would use at @ian_m's  drop checker, my personal opinion is that relying on a pH probe is a recipe for inevitable disaster.

cheers Darrel


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## ian_m (15 Nov 2019)

If you still want to make your own pH measurement system here is one of the definitive articles on how to interface to a pH electrode.
http://www.ti.com/lit/an/snoa529a/snoa529a.pdf

The critical thing is about 60mV/pH @ 25C and 75mV/pH @ 100C. A gnat attempting to squeeze a fart @ 100 meters will interfere with signals at these levels if you are not careful...


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## Andrew Butler (16 Nov 2019)

Thanks for your input @ian_m 


ian_m said:


> So easily done for £500 or less


You can get the baby version of the Neptune Apex which has this included at that price range and I think the probe fits into what's been described.
This is more money than I want to spend out, especially if it's not going to be reliable - it's just a waste of money, simple. It was never to control the CO2 but just give me something quick and easy to gauge from that would also possibly allow me to do away with the drop checker long term. I don't mind calibrating, that's not a huge effort if you have the solution(s)

To surmise, there's no way for what I deem sensible money to source a meter that will continually monitor CO2 levels in the aquarium.


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## zozo (16 Nov 2019)

The cheapest solution to position the probe correctly in my experience was putting the probe inline like this.





I kept this setup active for a few years and used 10 Litre CO² with it.

Funny was if the probe was placed in the aquarium the readings were always quite erratic and false. I don't know why, it might be a pottential difference created by the volume of the water.

Inline like this it was stable and as far as i could compare it with the CO² dop checker next to it accurate enough to be trustworthy.


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## papa_c (16 Nov 2019)

Hey Andrew, I have my tank running seamlessly from a Raspberry Pi for the last couple of years. I have a central rPi controlling dosing pumps, lights, C02, thermostat and 24/7 ph logging with a cheapo ebay probe that has been in the tank for 2 years and never lost calibration. I test it on bi monthly basis in 4.0 and 7.0 ph solutions and it is within the .05 accuracy. As mentioned early it is required to electrically isolate the ph Probe otherwise you will not be able to get readings. 

rPi is the backbone of the tank control with API's enabling remote control CO2, light, macros and micros. This interfaces/logs in to my home MSFT server 2016 which runs a website allowing me to view the tank real-time parameters and system control on phone or PC. originally this was hosted on a second rPi in place of the full MSFT server.

Check out Atlas Scientific website for pH starter kits as they support arduino and rPi, but you will need to be able to view data hence the need for the website.

While this started as a mini project it rapidly grew once confidence grew on the capability of the rPi to run the tank. I would suggest that this approach requires an advanced level of IT skills due to the coding, website building and server management.

I would estimate the "end solution" cost me about £300, but that is excluding the various upgrades to it. Being an eternal tinkerer the interest has outweighed the cost and i believe what I have far exceeds any commercially available product! But then I am biased


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## dw1305 (16 Nov 2019)

Hi all, 





Andrew Butler said:


> ...there's no way for what I deem sensible money to source a meter that will continually monitor CO2 levels in the aquarium.


I think the "continual" bit is the issue. Any system that works by the continual leakage of ions is going to give problems long term, so you really need to use a solid state option, and to keep it isolated from electrical interference (like Marcel's @zozo option).

You can get "standard" meters and probes that will give you accurate measurements, but you really need to re-calibrate them fairly regularly, and store the electrode in the appropriate storage solution.

If you have very heavily carbonate buffered water (or very salt rich water) then the problem lessens, as you move towards pure H2O the problem intensifies. The issue then is that you then know the pH is going to be pretty close to pH8 in heavily carbonate buffered water, and it isn't going to change very much.

Because I use rain-water (about 120 microS),  I'm not a CO2 user, run low nutrient and have very "weedy" tanks, I can predict the pH level in the tanks, but they don't really tell me anything that I didn't already know. During the photoperiod the tank is fully saturated with oxygen,CO2 depleted and the pH is somewhere around pH8, first thing in the morning it is around pH7 (more CO2, less O2). I have shell attrition on the snails, so sometimes pH must dip below pH7.  As flow reduces the amplitude of the variation will rise. It is back to <"the pond"> scenario. 





dw1305 said:


> <"Diel Variation Related to Thermal Mixing in a Subtropical....">


The <"Sands-Jensen paper">, linked into <"latest pH profiles">, makes interesting reading.

*Some methodology bits*
When I started searching for a standard set of methods, and parameters, that allowed you to characterise the health of your aquarium I actually started with pH, because it is so important. I hadn't realise how much pH would vary over a day, and I didn't know that CO2 injection was a thing.

When I found out about the pH drop from CO2 injection I knew I needed to look at pH measurement and stability slightly differently and after a while I began to think that actually I needed to abandon pH measurement all together, which led me to looking at conductivity, nothing like as useful, but easily consistently measurable with relatively cheap kit. 

It was the same with nitrate (NO3) measurement, I really want to know what NO3 levels were in the tanks, but it rapidly became apparent that there were issues with NO3 measurement. That was what why I went back to the _Lemna_ bioassay, re-configured as the <"Duckweed Index">.

cheers Darrel


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## Andrew Butler (16 Nov 2019)

zozo said:


> Inline like this it was stable and as far as i could compare it with the CO² dop checker next to it accurate enough to be trustworthy.


I'm going for a built in sump/filtration system so nowhere to fit it inline aside from just after the return pump which is where the CO2 is being injected.
@papa_c I looked to this and maybe even using a PLC for everything but I've everything else under control easy enough with smart plugs, lights with controllers and a pump with flow control which made me look away from that idea.


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## zozo (16 Nov 2019)

`My issue with the sump was the pump to close to the probe, most like both heaters also had some negative effect.

But there are e few different approaches available of different Ph meter designs on the market. Since they are electronic devices it uses an anode - and kathode + to calculate the value of pH. Most probes are 2 in one and i experienced them more susceptible to interference. Most likely because both are very close together.

Some Hanna and BlueLab meters (And others) use a different approach and separate it. I'm not sure which is what but they have a probe and a separate titanium pin. For convenience, i call it the ground pin. 

Anyway i had a Hanna and experienced this as a rock-solid meter and the only one i could use in my sump.
All other meter with a single probe and no G pin all went nuts. Also noticed the Hanna meter used a stronger current and voltage. It likely needs this to bridge the connection between probe and pin. The single probe types use Milli volts.








I actually noticed sticking a finger in the sump with the pH meter in it and touching the ground and the hairs on my arm stood up. Then i started measuring with a multimeter. The Hanna pH meter was definitively measurable while the Milwaukee always going nuts was not.

With in a sump this current likely is enough contained not to go to the fish tank. Since it has a significant measurable current running between pin and probe it is very stable and not susceptible to interference but i'm not sure the fish will like if it is placed in the aquarium.

These meters are also a bit higher in the price range.


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## Wookii (17 Dec 2019)

Andrew Butler said:


> I'm going for a built in sump/filtration system so nowhere to fit it inline aside from just after the return pump which is where the CO2 is being injected.
> @papa_c I looked to this and maybe even using a PLC for everything but I've everything else under control easy enough with smart plugs, lights with controllers and a pump with flow control which made me look away from that idea.



I wanted to monitor Ph wirelessly, and more importantly have the results easily graphed in an app, so I've just treated myself to one of these (an early Christmas present from me to me lol):

https://www.hannainstruments.co.uk/...ectrode-with-bluetoothr-smart-technology.html

It's blue-tooth, wireless (500 hour battery) so you need to be in range to log the data (there is a dedicated Hanna app), but I'll just leave an old iPhone plugged in near it, with the app running, to record the data.

It still needs recalibrating regularly to maintain accuracy (Hanna advise weekly), but I'll see what the drift is like over time. It looks to be a pretty accurate unit out of the box at ±0.005 pH, so as long as it stays accurate within the ±0.05 pH it'll be sufficient for me - and I'll see how long it maintains that lower spec accuracy and recalibrate based on that interval instead.

There are a few variants, including one in a titanium tube for beer if you wanted something more durable - but they all use the same sensor bulb I believe. I don't know what their lifespan is like, but their applications suggest they are robust enough for ongoing monitoring. Certainly when speaking to their tech support, they suggested longer term monitoring would be fine, but just reiterated that the sensor would need regular cleaning and recalibration to maintain accuracy.

Personally I plan to just get a profile over 48 hours, and then recheck that profile every month or two to ensure it is consistent, as reinforcement for dropper checker monitoring (keeping it in storage solution in between). As Darrel says, I personally wouldn't rely on it for CO2 levels, but it will be nice to see the actual Ph effect - and I'm a massive geek for gadgets like this!


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## ian_m (17 Dec 2019)

Nice, but....

Not sure you will get anything near +-0.005pH in a tank with ANY electrical equipment connected as 0.005pH is a change of 0.3mV which is equivalent to "a fish fart at 10cm" in electrical terms. . Better to take a water sample in a cup and measure that away from the tank. Getting pH electronics more accurate the 0.5% is hard, which in the above probe is about 0.05pH.

But does look useful, especially the connectivity to phone. Let us know how you get on.


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## dw1305 (17 Dec 2019)

Hi all,





Wookii said:


> I wanted to monitor Ph wirelessly, and more importantly have the results easily graphed in an app, so I've just treated myself to one of these (an early Christmas present from me to me lol):


I'm very interested in how this goes as well.





ian_m said:


> Not sure you will get anything near +-0.005pH in a tank


I don't think you will either, but even if it was +/- 0.1 I'd be happy.

cheers Darrel


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## Wookii (17 Dec 2019)

ian_m said:


> Nice, but....
> 
> Not sure you will get anything near +-0.005pH in a tank with ANY electrical equipment connected as 0.005pH is a change of 0.3mV which is equivalent to "a fish fart at 10cm" in electrical terms. . Better to take a water sample in a cup and measure that away from the tank. Getting pH electronics more accurate the 0.5% is hard, which in the above probe is about 0.05pH.
> 
> But does look useful, especially the connectivity to phone. Let us know how you get on.



Yep agreed (love the fish fart analogy lol). I personally have no requirements for it being that accurate - I'm more interested in approximate changes and profiling those changes over time in the tank itself, rather than accurate absolute measurements. The +/- 0.005 Ph is just the listed specs. I believe these are sold for lab use also, so I'm sure they must be able to achieve that accuracy, but I just wanted a wireless unit with data logging/graphing, and that is the only unit I could find - if they'd had a cheaper unit available with only +/-0.05 (or even +/- 0.1 as Darrel suggests) accuracy, I'd have probably got that instead.


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## Andrew Butler (17 Dec 2019)

ian_m said:


> a change of 0.3mV which is equivalent to "a fish fart at 10cm"


love the analogy! 

Cheers @Wookii I'm going to get things sorted on the tank/hardscape front first and see what money I've left over. Sounds very interesting though; keep us updated.


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## jaypeecee (19 Dec 2019)

Wookii said:


> It still needs recalibrating regularly to maintain accuracy (Hanna advise weekly), but I'll see what the drift is like over time. It looks to be a pretty accurate unit out of the box at ±0.005 pH, so as long as it stays accurate within the ±0.05 pH it'll be sufficient for me - and I'll see how long it maintains that lower spec accuracy and recalibrate based on that interval instead.



Hi @Wookii 

Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH? Not that there's anything wrong with calibrating to two decimal places.

JPC


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## Andrew Butler (20 Dec 2019)

jaypeecee said:


> Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH?


If you calibrate something with a solution that is for example 4.01 then that solution is essentially 4.010 or to exaggerate 4.010000000000 so I'd imagine that's where the third decimal place come from. Hannah produce some top quality equipment and I didn't see this earlier in the year when looking on their site. There is of course margin for error but this is just to try and answer your question here.


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## jaypeecee (20 Dec 2019)

Andrew Butler said:


> If you calibrate something with a solution that is for example 4.01 then that solution is essentially 4.010 or to exaggerate 4.010000000000 so I'd imagine that's where the third decimal place come from. Hannah produce some top quality equipment and I didn't see this earlier in the year when looking on their site. There is of course margin for error but this is just to try and answer your question here.



Hi @Andrew Butler 

Sorry, but I think what you are saying is incorrect. If a solution is calibrated to nominally 4.01, then it could be up to 4.014 but, when rounded up to two decimal places, that would be 4.01. It would have to get to 4.015 before an instrument would round it up to 4.02. I know that Hanna produce some excellent gear. Indeed, I have some of their test equipment. I suspect that the information published by Hanna is an error. If it was that important, I'd contact them.

JPC


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## jaypeecee (20 Dec 2019)

Andrew Butler said:


> I'm wondering if anyone knows of a tested device they use for continually monitoring the PH levels in their aquariums? I've a half decent Hanna pen already but should have the space to hide a probe and have the display in cupboard which would allow me to keep a rough eye on things easier. I'm not looking to spend crazy money but likewise don't want one that's either an absolute load of rubbish or I need a lottery win to purchase.
> I've found a few while looking though but nothing is jumping out at me, I realise it will quite possibly not just be PH Any suggestions welcome.



Hi @Andrew Butler 

Me again!

I agree with the reservations of others about continuous pH monitors. That's why I would be very hesitant about using one of these to control CO2 injection. OK, with that caveat in mind, have you taken a look at the PINPOINT® range of monitors? They produce some very interesting aquatics products, albeit (as their name suggests) geared towards marine aquaria. Here's the link:

https://americanmarineusa.com/collections/pinpoint-monitors

JPC


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## jaypeecee (20 Dec 2019)

Hi @Andrew Butler

Me yet again!

I have many times been very tempted to purchase a data acquisition device for data logging. It's only because I have so many other projects 'on the go' that it hasn't yet happened. Anyway, there is a low-cost versatile product made by a company called _pico Technology_. It is known as _DrDAQ_ and will accept a pH probe or ORP sensor input. It is supplied with the free _PicoLog_ software. Here is a link:

https://www.picotech.com/data-logger/drdaq/overview

JPC


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## Andrew Butler (20 Dec 2019)

jaypeecee said:


> I agree with the reservations of others about continuous pH monitors. That's why I would be very hesitant about using one of these to control CO2 injection


I've made no mention that this has ever been my intention; merely to have a rough idea how the CO2 levels change over a 24 hour period and longer.


jaypeecee said:


> Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH?


I appreciate there's always margin for error and results also rely on 'ideal' conditions; Hanna do make a 'Millesimal Buffer Solution' which is accurate to ±0.002
so could possibly support the ±0.005 of the HI-11102 HALO device although I'm just guessing here.

I think if I need a device this would be more than accurate for my needs and is only to keep an eye on the CO2 levels and monitor them out of interest as much as anything else.
Thanks for your input though


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## dw1305 (20 Dec 2019)

Hi all,





jaypeecee said:


> Something's amiss. The Hanna buffers permit calibration to two decimal places so how can they then claim that it's accurate to three decimal places, i.e. +/-0.005pH? Not that there's anything wrong with calibrating to two decimal places.





Andrew Butler said:


> There is of course margin for error but this is just to try and answer your question here.


I've been thinking about this, and I may be wrong,  but isn't there a more fundamental issue, which is that the decimal places on pH values can differ by several orders of magnitude, because pH is a -log^10 scale representation of the hydrogen ion activity?

I think that implies that the 3rd decimal place at pH4, is the same as the unit at pH7? You've gone through three orders of magnitude, from 10^-4 to 10^-7.

When-ever I think that I understand pH something else comes up that makes me think I don't at all.

This is a "weak acid / weak base" <"titration curve">. I think that is where we are when we add CO2, to 4dKH solution, and the bit we are interested in is somewhere around the equivalence point.  




 
cheers Darrel


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## papa_c (20 Dec 2019)

Must admit I'm enjoying reading the debate...however are we really concerned about measureong ph to the 1/1000th when we does EI based on teaspoon measurements!

Sledgehammer and walnut springs to mind


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## jaypeecee (20 Dec 2019)

papa_c said:


> Must admit I'm enjoying reading the debate...however are we really concerned about measureong ph to the 1/1000th...



Hi @papa_c 

There is no debate. Just a discussion and exchange of ideas. And I, for one, have no need for *actually measuring* pH to an accuracy of +/-0.001.

JPC


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## jaypeecee (20 Dec 2019)

Andrew Butler said:


> I've made no mention that this has ever been my intention; merely to have a rough idea how the CO2 levels change over a 24 hour period and longer.



Hi @Andrew Butler 

Apologies. I am fully aware that you had no plans to use the pH monitor to actually _control_ CO2 injection. I obviously implied otherwise. Have you had a chance to look at some of my suggestions?

JPC


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## Andrew Butler (21 Dec 2019)

jaypeecee said:


> have no need for *actually measuring* pH to an accuracy of +/-0.001


Completely agree with you here, I guess just the more accurate a device is the less margin for error.


jaypeecee said:


> Have you had a chance to look at some of my suggestions?


I've had a very quick look but need to sit down next year and have a proper look through them, thanks though.
I do see the Hanna bluetooth version as something that could work for me; I just need to look into things a bit more as money soon starts getting out of hand and I could just use my handheld.
Very interested to look into options as I'm in no rush.


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