The Proper Use of pH Controllers - finding consensus

[Art]

I think it may be helpful to the community to find a consensus regarding how to estimate CO2 in the water column in CO2 supplemented tanks. Essentially, when do you know you have enough for your tank and how to stay there consistently?

I am BY NO MEANS implying that I have the answer. I’m sure there will be different perspectives that equally lead to a successful aquarium. However, I’m interested to see if we can find a general consensus that can be used as the basic thinking for newcomers and experienced aquatic gardeners.

Some initial assumptions - do you agree with them? Am I missing any?

• We are not considering the keeping of livestock that may need a specific pH range.
• We believe the zero KH / pH drop fear is a myth that has been proven not to be a concern.
• KH is something that varies in the aquarium given the impact of substrates, natural biological processes, hardscape, etc.
• Directly measuring CO2 in the water column is something out of reach for most aquarists so the goal is an estimate measure.
• A true drop of ~1 pH point is a rough estimate of “enough CO2” or at the very least a good starting point.
• You can accurately deliver a specific amount of CO2 using CO2 flow meter.
• Chasing a specific pH is not ideal.
• Substrate used doesn’t matter.

Initial working formula for the proper use of a pH controller to provide CO2 in a planted aquarium:

1. Use a quality pH controller that is properly calibrated.
2. Measure fully degassed water sample from the aquarium to establish a good estimated degassed pH.
3. Set your pH controller to turn off the flow of CO2 at 1 point drop from the degassed pH (“pH bottom”).
4. Begin CO2 flow 1 hour before lights on. The pH bottom should be hit within 1 hour so adjust needle valve accordingly.
5. Observe livestock for signs of stress when pH is at its low point.
   • If livestock is stressed, adjust pH bottom to .1 less than the 1 point drop.
   • If livestock is not stressed, adjust pH bottom to .1 more than the 1 point drop.
   • Continue daily to find the point when livestock is not stressed and pH bottom is at its lowest.
6. Continue observation of livestock to ensure no changes over the next week.
7. Test pH probe monthly and calibrate as necessary.

Please post your thoughts, comments and experiences even if you completely disagree. Our goal is to try to refine the above until a general consensus is achieved.

List of pH controllers being used by the community:

• APEX Controller
• Milwaukee pH Controller
• CoralVue pH Controller
• American Pinpoint Marine
• GHL Profilux Controller

 

[GreggZ]

Art I have LOTS of thoughts on this, but will need to get to them later.

But you missed one controller, the American Pinpoint Marine. Rock solid unit.

 

[Ed Wiser]

I use a GHL Profilux controller.
It’s an industrial aquarium controller.

 

[Burr740]

One thing I think is often overlooked or never mentioned is that you need a rock solid KH to effectively use a PH controller for your CO2.

Folks using aquasoil type subs that buffer KH should not use one. The only exception is if your also using RO water and running a zero KH, like Gregg used to do when he had soil via RO water. If you have zero KH then there's no problem

But otherwise your co2 levels will be all over the place between water changes as the soil gradually lowers the KH through the week

Now some of you are probably thinking...wait Joe, what?? I see a tons of folks using a PH controller with aquasoil!

Well let me show you why thats a horrible idea

Most of us know these KH/PH/CO2 charts cant be relied upon to calculate co2 levels. But it is a perfect illustration of what happens if you have CO2 tied to a specific PH and the KH is changing:




Lets take an example: Say you use tap water and it has a KH of 5, and you also have an aquasoil type sub. Right after your water change lets say your KH is now 4 (because the soil has lowered whats left in the tank by a few degrees and you just filled it back up with 5 KH water)

Assuming a 4 KH lets say you have your PH controller set to 6.6 for roughly 30 ppm of co2. These numbers dont matter, what matters is to see what happens if CO2 is tied to a set PH and the KH changes

Two days later when the soil has dropped KH by a point down to 3, all of a sudden you have 23 ppm of co2 in the water if co2 is still tied to 6.6 PH. Four or five days later when the soil has dropped KH by another point down to 2, you are now rolling with 15 ppm of co2 in the water.

See how wildly CO2 levels can fluctuate at the same PH level if the KH changes at all?

This is why you MUST have a rock solid KH that doesnt change if you are going to control your co2 via the tanks PH level

 

[Art]

Art I have LOTS of thoughts on this, but will need to get to them later.

But you missed one controller, the American Pinpoint Marine. Rock solid unit.

Updated. Thanks for reminding me of that one. It was my first controller back in the day.

 

[Art]

@Burr740 thank you for bringing this up. It’s the point I was hoping to flesh out here.

Let’s assume that degassed (in tank) pH is 7 and we are dropping pH by 1 point to 6 every day via CO2. The controller is turning off the CO2 when pH reaches 6. I’m using Aquasoil (1+ year old) and tap water KH is 3.

Two questions:

1. Assuming average KH of the tank is 2 due to weekly water changes, I conclude that the CO2 in this aquarium would be about 60 ppm after a water change and, over the week, it would decrease to 30 ppm or less if I got to zero KH. My question is, is this a bad thing provided your livestock is OK?
2. Second question is, except in a zero KH environment, isn’t this CO2 concentration change the same for all CO2 delivery methods? Is there an alternative method that provides for a more accurate or static CO2 concentration if you do have KH in the aquarium?

Thanks for the thought exercise and I love the reference to The More You Know!

 

[Art]

*Adding to my post above.*

Some of you may know a site by an aquatic gardener called Marcel. He did some experiments on proper CO2 management and how 15 ppm of CO2 is what we should aim for to be safe. I fall into what he calls a choker as my CO2 is significantly above his recommendations. It does make for interesting reading and really has some interesting information on CO2 in aquariums.

I don’t want to change the focus of this thread to being about what is the proper CO2 level in planted aquariums. The focus is on using a pH controller to manage CO2. However, CO2 level is an important part of the discussion because it informs what we are trying to do with the controller.

 

[Count Krunk]

To ask a simple question, rodi that is adjusted with ferts will have 0kh?

As that is my plan, with bdbs.

 

[Burr740]

@Burr740 thank you for bringing this up. It’s the point I was hoping to flesh out here.

Let’s assume that degassed (in tank) pH is 7 and we are dropping pH by 1 point to 6 every day via CO2. The controller is turning off the CO2 when pH reaches 6. I’m using Aquasoil (1+ year old) and tap water KH is 3.

Two questions:

1. Assuming average KH of the tank is 2 due to weekly water changes, I conclude that the CO2 in this aquarium would be about 60 ppm after a water change and, over the week, it would decrease to 30 ppm or less if I got to zero KH. My question is, is this a bad thing provided your livestock is OK?
2. Second question is, except in a zero KH environment, isn’t this CO2 concentration change the same for all CO2 delivery methods? Is there an alternative method that provides for a more accurate or static CO2 concentration if you do have KH in the aquarium?

Thanks for the thought exercise and I love the reference to The More You Know!

Good questions Art. I dont know the complete answer to #1 but here's my thoughts on it

One train of thought is if we assume that 30 ppm is your floor, and that 30 ppm is above a limiting level for the plants. Then on paper we can assume that the plants are always getting what they need and anything above 30 ppm is just gravy and doesnt matter. Same principal EI dosing is based on.

Is that true? Idk. Is co2 entirely passive? Meaning it can it be at 40 ppm or 400 ppm and the plants will uptake the same amount, the minimum they need and no more.

Ive tried 2 point drops in fishless tanks a few times. You know just to make SURE co2 was "good" and not worry about it. Because all you ever hear in this hobby is that co2 can never hurt anything and nobody ever worries about that

Every time within a week or two things started going badly and a few species always turned south. (Digressing here, I know) Im not trying to get into the whole "Is there such a thing as too much CO2?" debate. But it does make me question if plants actually wind up with more inside them, good or not, when concentrations are higher

On a smaller scale would say 60 ppm be similar to an athelete on steriods when 30 ppm is the standard for general good health? Again I dont know. But my test runs make me wonder if co2 is entirely passive. And if its not, if going from 30 to 50 or 60 causes a different response from plants, then it lends further credit the accepted notion of how important having stable co2 is, whether its high or low

2. There is no stable delivery system if co2 is tied to a set PH and the KH is changing. Because there is no way around the controller cutting on and off more or less frequently as the KH moves (because the base level ph also changes). And just look at the chart to see what a difference a mere 1 degree change in KH does to co2 that is locked into the same PH

The only stable delivery method is one that doesnt change the flow rate or volume being injected into the tank. PH controllers do change that if the KH moves. Theres really no getting around it

There's a reason ADA doesnt put out PH controllers along with everything else they produce

 

[Burr740]

To ask a simple question, rodi that is adjusted with ferts will have 0kh?

As that is my plan, with bdbs.

It should have a zero KH unless you add something specifically to raise it, like potassium carbonate or calcium carbonate.

None of the nutrient salts have an affect on KH, including Ca and Mg (as long as you dont use K or Ca carbonate)

 

[CarlP]

Jumping on the subject on CO2 controller.
My next aquascape is going to be composed of Seiryu stones and lot of driftwood.
The stones are really reactive in vinegar and the water here is very soft. All that in conjunction with using CO2. I think my controller would have a hard time getting accurate reading from the water column with the KH changing over time.
Tell me if I’m wrong.
I’m using an Ista controller.

 

[Ed Wiser]

Good questions Art. I dont know the complete answer to #1 but here's my thoughts on it

One train of thought is if we assume that 30 ppm is your floor, and that 30 ppm is above a limiting level for the plants. Then on paper we can assume that the plants are always getting what they need and anything above 30 ppm is just gravy and doesnt matter. Same principal EI dosing is based on.

Is that true? Idk. Is co2 entirely passive? Meaning it can it be at 40 ppm or 400 ppm and the plants will uptake the same amount, the minimum they need and no more.

Ive tried 2 point drops in fishless tanks a few times. You know just to make SURE co2 was "good" and not worry about it. Because all you ever hear in this hobby is that co2 can never hurt anything and nobody ever worries about that

Every time within a week or two things started going badly and a few species always turned south. (Digressing here, I know) Im not trying to get into the whole "Is there such a thing as too much CO2?" debate. But it does make me question if plants actually wind up with more inside them, good or not, when concentrations are higher

On a smaller scale would say 60 ppm be similar to an athelete on steriods when 30 ppm is the standard for general good health? Again I dont know. But my test runs make me wonder if co2 is entirely passive. And if its not, if going from 30 to 50 or 60 causes a different response from plants, then it lends further credit the accepted notion of how important having stable co2 is, whether its high or low

2. There is no stable delivery system if co2 is tied to a set PH and the KH is changing. Because there is no way around the controller cutting on and off more or less frequently as the KH moves (because the base level ph also changes). And just look at the chart to see what a difference a mere 1 degree change in KH does to co2 that is locked into the same PH

The only stable delivery method is one that doesnt change the flow rate or volume being injected into the tank. PH controllers do change that if the KH moves. Theres really no getting around it

There's a reason ADA doesnt put out PH controllers along with everything else they produce

Joe it seems you are saying a basic drop checker is the way to go.
I always have one in my tank too.

 

[Art]

Thanks @Burr740 - thought-provoking response.

The only stable delivery method is one that doesnt change the flow rate or volume being injected into the tank. PH controllers do change that if the KH moves. Theres really no getting around it

I understand this. Assuming KH is not zero, anything that uses pH as the measure to dictate how much CO2 to release will result in unstable CO2 due to changes in KH. This is because KH changes will make the pH change.

Like you mentioned, if the facts are that 30 ppm of CO2 is the floor in your situation, then the question is one of too much CO2 present in the water. This is where you comment on active versus passive uptake is important. I have read that plants have a toxic level for CO2 but the amounts were quite high, if I remember correctly. This means that it may be a passive system but we are going down a rabbit hole here.

In my situation, I am assuming that 30 ppm is my floor (zero KH) and that 60 ppm of CO2 (KH 2) is not showing to be a toxic level for my plants and livestock. It is clear that CO2 is not stable in my system. The question is, does that matter? In my case, it doesn’t seem to be leading to algae outbreaks.

The other question your answer made me think about is: is there a method to provide stable CO2 delivery that doesn’t suffer from KH changes?

The only method I can think about is using @GreggZ method of using a CO2 gauge that allows you to provide a set amount of CO2. This means that CO2 delivery will be stable at whatever you set that gauge to. However, the amount of CO2 in the water will also vary as the KH in the aquarium changes. Just like with the CO2 controller. This isn’t a problem for Gregg because he runs with zero KH.

I wonder if combining the two systems wouldn’t be better? Using a CO2 gauge to provide a stable amount of CO2 but using a pH controller to turn off the CO2 at a set pH. Not ideal but perhaps more control.

If I win the lottery, I’m going to experiment by combining the Alkatronic with my pH controller and develop an algorithm based on the KH CO2 table to determine what pH to turn the CO2 off.

 

[Burr740]

I wonder if combining the two systems wouldn’t be better? Using a CO2 gauge to provide a stable amount of CO2 but using a pH controller to turn off the CO2 at a set pH. Not ideal but perhaps more control.

Unless I misunderstand what you mean, this doesnt solve the problem. Because while a flow meter should deliver a steady volume to the tank (just like a reliable regulator you just cant see the cc/min number), the problem is how often the PH controller turns the co2 on and off.

Its going to have the co2 turned on for longer periods of time at higher KH and for shorter periods of time as the KH drops. Because as the KH drops it takes less and less co2 to hit the target PH that determines when the controller shuts off. What this means is over the course of an hour or a day, there winds up being vastly different amounts of CO2 intrduced to the water, aka unstable co2

In your case since you theoretically never drop below the floor level, and your co2 only varies up in the non-limiting range, I think that is the best one can hope for. Like you said you arent seeing algae so as long as plants arent struggling it stands to reason that youre good

 

[Burr740]

Jumping on the subject on CO2 controller.
My next aquascape is going to be composed of Seiryu stones and lot of driftwood.
The stones are really reactive in vinegar and the water here is very soft. All that in conjunction with using CO2. I think my controller would have a hard time getting accurate reading from the water column with the KH changing over time.
Tell me if I’m wrong.
I’m using an Ista controller.

An accurate reading is not the issue. The controler should always give an accurate reading regardless what the KH does. The problem is when the KH changes the target PH for x amount of CO2 also changes. The controller doesnt know that. The controller doesnt know you want 30 ppm co2 in the water. It only knows to cut the co2 off at a certain PH

If you use the controller just to monitor what the PH level is there's no problem. The problem is when you tie your co2 to a specific PH number

 

[Art]

Jumping on the subject on CO2 controller.
My next aquascape is going to be composed of Seiryu stones and lot of driftwood.
The stones are really reactive in vinegar and the water here is very soft. All that in conjunction with using CO2. I think my controller would have a hard time getting accurate reading from the water column with the KH changing over time.
Tell me if I’m wrong.
I’m using an Ista controller.

Hey Carl,

So as you can see from the other responses, a pH controller isn’t foolproof. The stone in your tank will increase KH while driftwood and other items will decrease KH. This will cause your KH to vary, probably quite substantially.

While I think a pH controller will be useful to you, it needs to be just part of your strategy for CO2.

 

[Art]

If you use the controller just to monitor what the PH level is there's no problem. The problem is when you tie your co2 to a specific PH number

Understood.

May I ask how you manage your CO2?

 

[BigWave]

I am a firm believer of what the late "Wet - Carlos Flores" was trying to acomplish / do with his code. On his old website he wrote a drop checker program along with instructions on how to create drop checker fluid at certian degrees. For example 2dKH, 4dKH, 6dKH. The idea was to place 2 or more drop checkers in the tank either next to each other or apart. Each checker had a different dKH fluid in it. Depending upon the fluid dKH it would result in a different color of both checkers. You then compare the colors and the program spits out your exact CO2 concentration.

Here is his master repository of all the code he has written. FYI it is what quite a bit of the Rotala Butterfly Calculator is based upon. cflores memorial

Here is the code for his Drop Checker Calculator. You do have to compile it and run it yourself!

GitHub - flores/dropcalc: Calibrates CO2 checkers/Bromothymol blue-based pH kits for any given CO2 target by using NaHCO3

Calibrates CO2 checkers/Bromothymol blue-based pH kits for any given CO2 target by using NaHCO3 - GitHub - flores/dropcalc: Calibrates CO2 checkers/Bromothymol blue-based pH kits for any given CO2 ...

github.com

 

[Art]

Thanks @BigWave - how do you use this to better control CO2?

 

[BigWave]

Haha I dont know. I would assume its more of a better justification of the whole visual aspect of the drop checker in itself. Someone smarter or that can relate the data better would know. If what im visualizing and understanding is correct you can calculate concentration via the 2 different drop checker colors very accuratly. If one were to target exactly say 30ppm CO2 you would simply add this dKH to the 1st checker and this dKH to the 2nd. Once you see both colors you have met that goal.

I posted it becasue it does kind of go along with what @Burr740 and @GreggZ are talking about above. kH does play a huge role in the measure of CO2.