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Well I currently have 9 tanks with co2, and if I ever get fancy on one I wanna do them all lol. So I keep it simple. I try to hit about a 1.3 drop in PH, set the regulators to whatever does that, and thats it
All you need is a steady means of delivery that remains the same from one day to the next. Doesnt matter if you control it with a flow meter or regulator. As long as its the same all the time.
The KH in my soil tanks can change all it wants to, because the co2 rate never does. And that is where PH controller become troublesome with a KH that changes, because they do alter how much co2 a tank gets whenever it changes
This thread makes a very valid point that pH controllers are only useful when the KH in the tank is stable. So when substrate is buffering (probably this effect goes away when the substrate gets older), or with rocks and hardscape that changes water hardness, a pH controller is a no go.
My tank has a stable KH, even more so as I change water 70% weekly and the tap is pretty stable with some minor variations depending on the season in HK and sourcing of water. With that, I used an inexpensive controller for several years and stabilised pH within a few hundredths. If I would have to buy a lab grade regulator that would give same stability over time, I would spend much more than on my controller. So I see the controller as a cost efficient tool to provide really good stability, and with a better possibility to make small adjustments even than with high end regulators.
I am now using my horizontal reactor in overflow mode, so do not depend on precision for my regulator or on a pH controller anymore.
An often mentioned argument against pH controllers is that it includes a point of failure, where the malfunction could potentially gas the fish. When using the horizontal reactor we can have it inherently safe, as the reactor will simply dump the gas from the overflow when too much gets injected.
So I think I’m doing the same as you. I have been dropping a consistent 1.4 points and not worrying about the KH. Everything seems fine for me at the moment but this thread got me thinking about improving the situation.
I’m looking into programming my Apex so that it tries to track KH reduction. This way, as KH is reduced, the system will adjust the pH cutoff so that CO2 levels, at least theoretically, will stay close to the 30 ppm.
While I would love to tie that to a constant KH monitor, it’s not worth spending $$$ on this. I will spend a week measuring KH daily to establish a pattern and then assume it will be the same weekly.
Well, I see I can improve on the pH controller method in one of two ways:
1. Measure my KH daily for a week and then assume that any KH changes will be the same every week. For example, a 1 KH drop per day. I can then program my pH meter to adjust the pH daily to compensate for the decreasing KH. In this way, I can approximate maintaining a roughly 30 ppm CO2 level. Not ideal and I’m still measuring tank pH that may have other variables (ions) impacting the pH.
2. DIY a pH metered drop checker. This would use a pH probe to measure the pH of the drop checker solution. This is an improvement over 1 above because I’m not measuring tank water. Rather, I’m only measuring the KH solution that is only impacted by CO2. Therefore, it doesn’t matter what the tank KH is, the KH in the solution is static so I will always dose 30 ppm CO2.
The DIY drop checker is not a new idea. It was discussed back in 2009 but I don’t believe it was ever built. Probably due to too few having CO2 controllers back then.
I’m going to try to go for the second option unless one of you talks me out of it.
1. Measure my KH daily for a week and then assume that any KH changes will be the same every week. For example, a 1 KH drop per day. I can then program my pH meter to adjust the pH daily to compensate for the decreasing KH. In this way, I can approximate maintaining a roughly 30 ppm CO2 level. Not ideal and I’m still measuring tank pH that may have other variables (ions) impacting the pH.
The more complicated the 'solution', the higher the chance that something goes wrong. Small errors, or inaccurate assumptions, could easily make the cure more dangerous than the disease.
2. DIY a pH metered drop checker. This would use a pH probe to measure the pH of the drop checker solution. This is an improvement over 1 above because I’m not measuring tank water. Rather, I’m only measuring the KH solution that is only impacted by CO2. Therefore, it doesn’t matter what the tank KH is, the KH in the solution is static so I will always dose 30 ppm CO2.
One could make a drop checker with pH probe, but it will react too slowly (hours, not minutes) on changes to be a meaningful part of a controlled system. If your controller lags for an hour or so, you may already have gassed your fish with excessive CO2 injection.
I would really advise for (the minority of?) tanks that have KH instabilities, stay away from pH controllers for CO2.
Note for innovative manufacturers: Some time ago I hinted that it is possible to completely rethink CO2 injection and mentioned at the time that amongst others it could eliminate the risks of KH changes. This thread highlights again that we may have an opportunity to serve the hobby with new technologies.
One could make a drop checker with pH probe, but it will react too slowly (hours, not minutes) on changes to be a meaningful part of a controlled system. If your controller lags for an hour or so, you may already have gassed your fish with excessive CO2 injection.
The type I’m doing is different than the traditional. I’m doing a membrane type that doesn’t have the air space. It also uses a thin but large KH solution. Together they offer a much quicker reaction time.
As a back up, my system uses a second pH probe in the tank that will shut off CO2 if things go wrong.
The type I’m doing is different than the traditional. I’m doing a membrane type that doesn’t have the air space. It also uses a thin but large KH solution. Together they offer a much quicker reaction time.
If it works, it would be fantastic. Really interesting experiment, even if it would be too slow for a CO2 controller you may have created a good CO2 probe that is both accurate and independent (assuming membrane does what you expect) of tank chemistry.
I agree to a point. We can take this just a bit further. Much depends on the level of dKH and the dKH swing. In higher dKH tanks small swings don't make much of a difference, but in very low dKH tanks the swings are quite large.
Since I like to visualize things here's a quick spreadsheet showing the CO2 concentration change at various dKH levels. The row in blue is the CO2 ppm at the stated numbers. As you can see tanks with very high dKH don't have much to worry about with one or two point swings. As dKH comes down the CO2 ppm swing becomes larger. But still not too bad if you keep an eye on your levels and adjust.
And then when you get to a pretty low dKH like 2 the swing are more drastic. So just saying you need to know what you are dealing with when you decide if a controller will work for you.
Years ago when I first went with RO water I would raise dKH to 2. My substrate was BDBS so the dKH stayed rock solid. Perfect for a pH controller.
Then I swapped for Landen. Then my dKH would drop from 2 to almost zero pretty quickly. This was NOT good for a controller. That is when I decided to stop dosing any carbonates and stop fighting the change.
So yes pH controllers are best for tanks with steady dKH, but can be used in tanks that have some small fluctuation, especially if you test dKH on a regular basis and adjust as needed.
Of course in a perfect world use RO and control everything. Then a controller is a great tool. Personally I wouldn't be without one. Makes fine tuning CO2 very easy. If I want to bump things up a bit, I can easily dial in accurate small changes. I usually go in 0.05 increments then observe. Then just set and forget. Also serves as a fail safe for my expensive and hard to replace Rainbow fish.
As far as I know, @plantbrain found that the response time was too slow. This would still make it a valuable instrument, but probably not useful for using with a pH controller. In my estimation you would need response times of minutes, or less, for the probe to be useful in combination with a pH controller. When the probe is too slow, it will be impossible to control CO2 within a 0.1 pH bandwidth.
If we can find an innovative manufacturer to develop the next generation CO2 control, I may have some ideas . Engineers could build a prototype in a week, I could help to work out the math for the controls. It does not need new technology, like a new probe, it is based on a new control concept with existing technologies, and software. We could form a small working group with the manufacturer, and go for it. The biggest hurdle is not technology, but it is the commitment to innovation.
The type I’m doing is different than the traditional. I’m doing a membrane type that doesn’t have the air space. It also uses a thin but large KH solution. Together they offer a much quicker reaction time.
As a back up, my system uses a second pH probe in the tank that will shut off CO2 if things go wrong.
So here is what I’m thinking. A rectangular acrylic box with a pH probe compression fitting on the top allowing the probe to go down into the solution. The solution would be as little as possible to properly cover the tip of the probe to get readings. The bottom of the box would be Tyvek, a gas permeable membrane so that no air bubble is needed.
Given the lack of an air layer and using a very thin KH solution but spread out to have a high surface area, I’m hypothesizing that the solution will react more quickly than the normal drop checkers. Overshooting is inevitable but with relatively quick reaction time, it shouldn’t get too high.
Just in case, I have a separate pH probe that I will put into the tank to serve as a too high warning and CO2 shut off.
So you are wanting GHL ‘s KH director.
This is how GHL’s KH director works. Water ie pumped into a chamber then a reagent is introduced. I have had one for several years.
I would love it, @Ed Wiser, but out of my price range at the moment. I would tie it to my pH controller to vary my CO2 based on KH changes.
That being said, there are other ions that can impact pH in the aquarium. Therefore, I think isolating CO2 as the only thing impacting KH would be a better solution.
An this is why planted aquarium users don’t get the tech they want
All this tech has been available in the marine aquarium hobby for years now.
You can measure any element you want in a saltwater aquarium. In a continuous basis. It would all be available for planted tanks if users wanted it. I know the owner of GHL his is a planted tank keeper. He has already set up a monitor to do what everyone is wanting for his own aquariums. But doesn’t make it available for the general public because freshwater hobbyists will not pay the price for the equipment.
The only data point I found regarding the speed is about half an hour , which is better than a drop checker, but still at least a factor of 10 too slow for use with a pH controller.
But who knows, perhaps trying again with improved quality membranes will give better results. That makes the experiment really worth it imo.
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