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pH controller

Clare

Community Member
AquaGirls
Dec 9, 2022
32
15
NSW
Hello All,

I’m looking for ways to optimize my CO2 use.

I’ve got a reactor in the sump of my 850+L tank system. I use the drop checker to get an idea of CO2, but the lag annoys me, and I’m concerned about the CO2 swing during the day.

It’s tricky using the kH/pH method to calculate CO2 concentration, because the starting kH is so low, and starting pH is about 6.8.

I’ve got my hands on a pH controller, and am wondering how this is used in the planted tank C562192D-141E-4B5D-B682-368731C2F4C5.jpeg setting?

Thanks for any advice!
 
Good morning. Generally speaking, a pH controller is basically a secondary way of measuring CO2 levels.
To begin with, you really need to know what the degassed pH level of your source water. Simplest way to do this would be to collect a small amount of source water (1/2 cup?) and let this water sit for a few days to equalize with the atmosphere. Some will use a small air stone to speed up the process - may be useful. After a few days use your pH meter to check the pH of your source water - make note of the reading.

Generally speaking, a 1.0pH drop in aquarium pH equates to about 30ppm CO2. This is a good starting point for most.
Some of us run closer to a 1.3pH drop which gets closer to the borderline where livestock become uncomfortable.

The next challenge is properly adjusting your working pressure of the regulator and the needle valve to consistently achieve the same pH drop each day.
 
Last edited:

Description​

The Macro Aqua pH computer is a device necessary in every CO2 set. It regulates the dosage of CO2, and by means of continuous pH measurement in the aquarium water, it controls the level of this parameter at a constant, optimal level. Additionally, this device monitors the water temperature in the aquarium. It has automatic calibration.
Description
What does it do?
The pH controller is designed to regulate the supply of CO2 to the aquarium. Based on the pH readings from the probe, the computer stabilizes the pH value at a uniform, constant level. e.g; 6.8 pH.
About calibration and pH probe:
The Macro Aqua v2 pH computer measures with an extremely precise probe. It is possible thanks to automatic calibration in buffers with a pH value of 4 and 7. Thanks to this, the probe readings have a range of 0-14pH and an extremely small margin of error of indications of 0.1%. The computer itself can maintain the set pH value in the range of 3.5-10. Buffers are part of the kit.
PH and temperature display:
The pH measurement results are displayed on the LED screen with an accuracy of tenths. The temperature is displayed below. The housing is made of high-quality plastic, thanks to which the whole looks elegant and solid.
Mounting options:
The set includes a foot / computer stand and a hanger for the edge of the aquarium. In addition, the computer’s pH housing has installation holes, with which we can attach the controller to, for example, the wall of the cabinet and four large suction cups.
The probe has a separate hanger for the edge of the glass.
Included:
– Macro Aqua PHT2 computer
– manual in Polish
– pH 4 and 7 buffer (25ml in bottles with 50ml capacity, so you can insert the probe directly into the bottle)
– Macro Aqua probe
– probe hanger
– computer hanger and footer
– 4 suction cups
– 2 mounting screws (e.g. as a hanger for the inside of the cabinet)
– original packaging
Technical data:
– power consumption: 2W
– measurement accuracy: 0.1%
– measurement range: 0-14pH
 
I’ve got my hands on a pH controller, and am wondering how this is used in the planted tank setting?

Thanks for any advice!
In simple terms a pH controller turns the power to your CO2 system's solenoid on and off.

It does so by monitoring pH and using parameters that you set. I am not familiar with that unit but I can tell you how mine works.

My upper limit is 4.95 and my lower limit is 4.85. If the pH is above the upper limit of 4.95 the CO2 solenoid is powered on and the CO2 flows. When the pH reaches the lower limit of 4.85 the CO2 solenoid is powered off. So the pH remains in the band of 4.85 to 4.95 all day long.

One caveat is that you should have a stable dKH to use a controller. If dKH rises then the CO2 concentration would be higher if the upper/lower limits are not changed. This could be an issue with livestock so you need to keep an eye on the dKH.

In my case my dKH is always zero so controller works great for me.
 
To echo @GreggZ ‘s point, your KH must be stable in order to use a controller. I’ll use my tank as an example of one where you absolutely cannot use a controller, just to put some numbers to it…

My tank has around 200lbs of Seiryu stone in it, and my KH rises from around 2 after my water change to 4 by the end of the week. If I took a degassed sample of water from right after my water change, I would find it had a ph of around 7.3. If I set my ph controller to 6.2, that would give me a CO2 concentration of about 37ppm.

Now my KH goes up to 4 by the end of the week, but the controller is still pushing CO2 to a pH of 6.2. Per the pH/KH chart, KH4 / pH 6.2 is a CO2 concentration of about 76ppm. This would be very dangerous, or even deadly to my tank inhabitants.
 
Now my KH goes up to 4 by the end of the week, but the controller is still pushing CO2 to a pH of 6.2. Per the pH/KH chart, KH4 / pH 6.2 is a CO2 concentration of about 76ppm. This would be very dangerous, or even deadly to my tank inhabitants.
Exactly! If your dKH is not stable then you need to regulate flow as precisely as you can.
 
I run my CO2 off of my apex controller via pH probe. To dial CO2 in I adjust manually using drop checker and general pH drop readings. Then I keep it there and set the controller to turn off if pH drops below that point. This way my CO2 rate is not so much that if the controller did not stop it I would still have acceptable CO2 levels, just a bit higher than what I want.

IMO it is dangerous to set CO2 injection rate really high and rely on a controller to stop at a certain pH. If you make a mistake or have unstable dkH parameters or whatever you will certainly gas your fish

I am not really too concerned about changes in dkH or whatever... My pH always drops around 1.2-1.3 throughout the day.

I also make sure to keep my sump at about the same level because if it gets too low there is significantly more surface agitation and off-gassing.
 
I don't think i would ever use a controller - i don't think the co2 reacts fast enough; i use a smart switch to have it on during the day and off at night. I use a monitor (examples include milwaukee, hydros, ghl, ....) to graph the co2 and get alerts if it gets too low. I also do not try to get anywhere close to 1 ph drop - my target is closer to somewhere between 0.5 and 0.75 as i find the fishes i keep get rather upset as it gets close to 0.75 (my base ph is around 7.0)
-
on a daily basis my ph range from 7.1 just before the co2 goes (~7:50am) on to 6.5 just before it shuts (6.50pm) off (I haven't actually calibrated the pen yet so the shift might be off a little - will calibrate it after i move).
 
Again, to each his own.

But the beauty of the controller method is that it is automatic. Properly set up it is quasi-homeostatic. For stability, this is as good as it gets. No bubble counters, no drop checkers. The pH probe occasionally requires cleaning and calibration, but that's it. Thanks, Gregg, for emphasizing that the method does require regulating a respectable alkalinity. It's sooo simple.

I have been holding KH in the jungle at 100 ppm, 5.6 degrees. This is long-term running average of daily tests. Here is the actual pH plot for the last week:
D5iLN5Q.jpg

This solid, highly stable 6.75 is maintained by the Apex pH controller. CO2 is a constant 30 ppm. Naturally there are transients due to practical aspects; all real dynamic systems exhibit transients. So we could say CO2 is 30 ppm, + or - approximately 2 ppm. This in no way invalidates the controller method. It is necessary only to assure that the set-up is right and the KH is stable. In principle, I can run this aquarium exactly this way forever, without fiddling with inherently unnecessary equipment. Here is the result (it may not be everyone's pick for style, but it is alive):
H3lRMrO.jpg
 
Thanks so much for all the advice. (Btw, I love the “jungle” look….I’ve attached a photo of each side of my crazy set-up. Lights are dimmed as was playing with sunset options ).

When I last checked (a couple of months ago) my kH was very low - 2 or 3 when I last checked. I tossed some shells in the sump, but doubt it’s brought it up much (thinking more kH would provide some buffer?):..and starting pH in the tank (not degassed water) is around 6.8.

I’ve only had a drop checker, and am a bit frustrated by the lag-time and lack of accuracy with it…..really it’s just been to check my CO2 cylinder isn’t empty!

My motiviation for a pH controller was to:
- bring in some accuracy to my CO2 use (enabling better titration)
- reduce the swings in CO2 - I’ve read that this can contribute to algae, which I am constantly at war with
- preferably be more efficient with CO2 use ie. The CO2 cylinder lasts longer!

More questions I’m afraid!….as a newb to all of this…:

…Some of you leave the CO2 on 24hrs with the pH controller - I’m wondering what the point is with this? Is it so you end up over all using less CO2 because you don’t need to “re-load” the tank before each “lights on” (with the tank requiring less CO2 to maintain the set pH when the plants aren’t photosynthesising during “lights out”)?

….in a tank with very low kH, to get 30ppm CO2 means very low pH in the tank. Wouldn’t this be a problem for the livestock?

- in a tank/sump set-up, does everyone just measure the pH in the return chamber of the sump (and perhaps note the difference between this and the display tank pH)?

Thanks for your advice!
 

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When I last checked (a couple of months ago) my kH was very low - 2 or 3 when I last checked. I tossed some shells in the sump, but doubt it’s brought it up much (thinking more kH would provide some buffer?):..and starting pH in the tank (not degassed water) is around 6.8.
2 to 3 dKH is not VERY low. Most people would love to have that soft of source water. In general most plants prefer lower dKH and no reason to raise it from that level.

I’ve only had a drop checker, and am a bit frustrated by the lag-time and lack of accuracy with it…..really it’s just been to check my CO2 cylinder isn’t empty!
Drop checkers are a rudimentary method of measuring CO2. You need to keep in mind it's basically a liquid pH test, which in general are poor measures of pH compared to a calibrated pH probe.

…Some of you leave the CO2 on 24hrs with the pH controller - I’m wondering what the point is with this? Is it so you end up over all using less CO2 because you don’t need to “re-load” the tank before each “lights on” (with the tank requiring less CO2 to maintain the set pH when the plants aren’t photosynthesising during “lights out”)?
Very few people I know run CO2 24 hours. There really is no need for it. Plants are not utilizing CO2 at night. In fact they are using O2 and expelling CO2.

….in a tank with very low kH, to get 30ppm CO2 means very low pH in the tank. Wouldn’t this be a problem for the livestock?
For the vast majority of livestock it makes no difference. I run my tank at zero dKH and drop pH to 4.85 daily via CO2 injection. I've got a tank full of Rainbow fish that are healthy, colorful, and long lived.
- in a tank/sump set-up, does everyone just measure the pH in the return chamber of the sump (and perhaps note the difference between this and the display tank pH)?
Once the CO2 is fully dissolved I doubt you find much difference between the readings. I've taken readings all over my tank testing the theory that CO2 dissolution can be different in different parts of the tank in the same body of water. The readings are always exactly the same.
 
My pH probe is in the display tank. I use an in-line diffuser at the filter effluent so water entering the tank is "loaded". Time of travel of laden water, or diffusion rate, if you will, so that the probe is detecting the pH change, is minimal. The needle valve at the injection point is set to nearly closed to minimize overshoot. These two time factors working together determine the magnitude of the pH swing for each solenoid turn-on event. These swings are the "transients" to which I refer. If not minimized, these stop being transients, which cannot be completely avoided as a practical matter, and become instead a pattern of periodic instability, which is definitely unwanted. This is what I refer to as the "set-up." If not done right the pH response will be extremely choppy.

The reason for leaving the system in automatic mode 24/7 is because you can. The solenoid will not turn on unless the system calls for CO2. If in the dark plants aren't using CO2 it will not be consumed and thus the solenoid will not turn on. What would be the point in manually switching it off? Also, CO2 can depart incidental to normal water movement, so pH will rise overnight. If the system is left in auto, the solenoid will turn on a few times to compensate. It's automatic!

In deference to those who are doing it differently, I concede that the KH and pH should be whatever they want them to be, regardless of their reasons. But, to make the fully automatic controller method work properly, have a dKH of at least 4. I cannot see the reason for skimping on the buffer. I keep my dKH at around 5.6 because I can get 30 ppm CO2 with a pH of 6.75. These values for pH and KH are good centerline parameters for all life-forms that interest me.
 
2 to 3 dKH is not VERY low. Most people would love to have that soft of source water. In general most plants prefer lower dKH and no reason to raise it from that level.


Drop checkers are a rudimentary method of measuring CO2. You need to keep in mind it's basically a liquid pH test, which in general are poor measures of pH compared to a calibrated pH probe.


Very few people I know run CO2 24 hours. There really is no need for it. Plants are not utilizing CO2 at night. In fact they are using O2 and expelling CO2.


For the vast majority of livestock it makes no difference. I run my tank at zero dKH and drop pH to 4.85 daily via CO2 injection. I've got a tank full of Rainbow fish that are healthy, colorful, and long lived.

Once the CO2 is fully dissolved I doubt you find much difference between the readings. I've taken readings all over my tank testing the theory that CO2 dissolution can be different in different parts of the tank in the same body of water. The readings are always exactly the same.
Oh I must have misunderstood your comment re how you run your CO2. So you don’t have it going all day, using the controller to alter the amount going in to the tank?
…do you have a timer on the solenoid and the controller?

….I was thinking it would still make sense to run it all over 24 hrs, because the controller would turn the CO2 off when lights were off, as the CO2 levels would rise from the plants etc (and pH fall)….Ie. The system doesn’t have a timer, but the controller will stop CO2 infusing when lights are off.
 
My pH probe is in the display tank. I use an in-line diffuser at the filter effluent so water entering the tank is "loaded". Time of travel of laden water, or diffusion rate, if you will, so that the probe is detecting the pH change, is minimal. The needle valve at the injection point is set to nearly closed to minimize overshoot. These two time factors working together determine the magnitude of the pH swing for each solenoid turn-on event. These swings are the "transients" to which I refer. If not minimized, these stop being transients, which cannot be completely avoided as a practical matter, and become instead a pattern of periodic instability, which is definitely unwanted. This is what I refer to as the "set-up." If not done right the pH response will be extremely choppy.

The reason for leaving the system in automatic mode 24/7 is because you can. The solenoid will not turn on unless the system calls for CO2. If in the dark plants aren't using CO2 it will not be consumed and thus the solenoid will not turn on. What would be the point in manually switching it off? Also, CO2 can depart incidental to normal water movement, so pH will rise overnight. If the system is left in auto, the solenoid will turn on a few times to compensate. It's automatic!

In deference to those who are doing it differently, I concede that the KH and pH should be whatever they want them to be, regardless of their reasons. But, to make the fully automatic controller method work properly, have a dKH of at least 4. I cannot see the reason for skimping on the buffer. I keep my dKH at around 5.6 because I can get 30 ppm CO2 with a pH of 6.75. These values for pH and KH are good centerline parameters for all life-forms that interest me.
Yes, this was what I have been musing about. And I thought slightly higher kH would help minimise crazy swings….

That being said, I’ve got a big volume of water with inevitable agitation via sump etc, so I’m not sure I could achieve dangerous CO2 levels….. (but the drop checker can get to yellow quite easily…..)

Thanks again for your help everyone.
 
You are correct. The higher KH minimizes the "crazy swings". The point is not merely to avoid dangerous levels, but to tame the transients so that the pH response will not be choppy. Fully automated means turning the solenoid on and off in response to crossing back and forth across a programmed threshold value. You will get transients. A reasonable amount of buffer resists pH change, thus providing a "cushion" to absorb sudden drops upon turn-on. A higher base-line KH value enables you to obtain a stable CO2 concentration at a comfortable pH. A dKH of at least 4 gives you some room to program a sane and sensible pH. You get still more room with 5. Testing and adjusting KH is really easy to do.

I am not pushing anything here, so do not construe my remarks as advice. I am showing that a full-auto CO2 system is possible and does work. But it is a specific methodology with protocols. If you trust your pH monitor, you don't need to consult a drop checker. With a very good quality needle valve you won't need the drop checker or the bubble counter. You will need to keep the pH probe clean and to check its calibration occasionally. This is an alternative method. Each method has its rules. Its largely a question of what rules you want to go by and in which equipment line-up you want to place your trust.

I like your aquascape. The wood is impressive.
 
Oh I must have misunderstood your comment re how you run your CO2. So you don’t have it going all day, using the controller to alter the amount going in to the tank?
…do you have a timer on the solenoid and the controller?

….I was thinking it would still make sense to run it all over 24 hrs, because the controller would turn the CO2 off when lights were off, as the CO2 levels would rise from the plants etc (and pH fall)….Ie. The system doesn’t have a timer, but the controller will stop CO2 infusing when lights are off.
My CO2 controller is on a timer. It comes on two hours before the light cycle and turns off an hour before it ends.

Like I said there really is no reason to run the controller at night. Let's take my tank as an example. During the CO2 period the tank is at a pH of 4.85. Once the CO2 controller is turned off near the end of the lighting period the pH begins to rise. By the time the CO2 come back on in the later morning it's at about 5.90 or so. If my CO2 controller were running at night my pH would remain at about 4.85 all night and I would be injecting CO2 all night long, which is a waste as plants are not using CO2 at night.

Yes, this was what I have been musing about. And I thought slightly higher kH would help minimise crazy swings….
Crazy pH swings are pretty much a myth. pH crashes are almost always tied to poor maintenance. Most of the best planted tanks in the world run very little to zero dKH. Plants prefer it. Most livestock doesn't care. It's an old myth but it dies hard. At beginner sites you will often see the irrational fear of low pH and pH crashes. They have fear because of what they have read not what they have experienced.

Here's a link to a good article about low pH tanks by my friend the 2hr aquarist. My tank is shown there when my dKH was at 1.00. Since then have been running it at zero for several years now.

 
*snip
Crazy pH swings are pretty much a myth. pH crashes are almost always tied to poor maintenance. Most of the best planted tanks in the world run very little to zero dKH. Plants prefer it. Most livestock doesn't care. It's an old myth but it dies hard. At beginner sites you will often see the irrational fear of low pH and pH crashes. They have fear because of what they have read not what they have experienced.
*snip
Along with “Dirty Tank Syndrome”, I’ve also heard the origins of the “pH crash” came from a beginner’s understanding of the interaction between carbonates, general hardness, and pH. Let’s look at this from the perspective of a non-plated tank fish novice…

Our Fauna become acclimated to a particular GH, and that number represents the osmotic pressures being put on each and every cell in their body. Taking a fish from dGH 15 water and plunking them into a 5 dGH tank will almost certainly result in the death of the fish. Now, when we’re talking municipal water, or groundwater in a particular location, it’s assumed that they’re going to have similar GH values between the fish store and the home tank.

Expounding from there, typical municipal or well water will also contain a specific amount of carbonate in the water, affecting the pH. What we normally see is an increase in GH will also present with an increase in KH. This isn’t true 100% of the time, but it’s good enough for the average aquarist.

From the fish-only world, and especially novice aquarists, water testing is a big taboo. They should be familiar with ammonia, nitrite, and nitrate testing, but that’s about it. When their fish suddenly die, the fish store will have them do a pH test to see what their pH is registering. The average fish store employee knows that water with drastically different pH **can** kill fish, but they don’t really know the **why**. It’s just assumed that the cause of fish distress is due to the pH.

The actual cause of death in these cases, where fish are put into water with a drastically different pH, isn’t the pH, or the KH of the water. It’s the GH of the water. A lack (or over abundance) of Calcium and Magnesium ions will affect the osmotic pressure of the livestock, and a sharp change can kill your fish.

The anecdote of the “ph crash” happens when a municipal water supply drastically changes the general hardness of their water. Aquarists don’t know what’s happening, go to the fish store, get told to check the pH, and come back with a very low pH (remember, GH and KH almost always go hand-in-hand). The fish death is blamed on a pH crash.
 
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