# pH Controllers...how to maintain a CO2 level AND pH level ?



## Antipofish (22 Feb 2012)

Hi
I have been looking at pH controllers which (i presume) control the solenoid to switch on the CO2 in order to maintain the pH at a desired level.  

My question is, "How do you maintain a set pH as well as maintaining a desired  CO2 level" ??


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## sWozzAres (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*

Program in your desired pH and the controller will do the rest. For instance, program in 6.9 and the controller will switch the co2 on if the pH is 7, and off if it gets to 6.8.

The trick though is to set the co2 up so that it never quite gets to 6.8 - otherwise the controller will be switching on and off throughout the lighting cycle.


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## George Farmer (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*

pH controllers are widely regarded amongst many planted tank enthusiasts as a waste of money and may actually do more harm than good.

They rely on the pH/KH/CO2 relationship to determine CO2 levels.

You need to test your KH (which is rarely accurate using most kits) to determine what pH your controller needs to be set to, by using a pH/KH/CO2 table.






When the pH controller detects the pH is too high it injects CO2 via a solenoid until the pH drops to the desired level.  When the pH is low enough, the CO2 injection is stopped.

The issue with this is that CO2 is not the only influence on pH in the aquarium. This is why we don't just rely on the pH/KH/CO2 charts to determine CO2 levels either.  Other acids from organic matter etc. in the aquarium will falsify results.

Also the nature of the pH controller continually switching CO2 on and off via a solenoid means that the CO2 won't be stable. Unstable CO2 causes algae.

The pH probe attached to the controller requires frequent calibration and if faulty can result in overdosing or underdosing CO2. At worst this may kill your livestock, at best cause you algae.

It is much cheaper and arguably more effective to use a long-term CO2 testing method such as a drop checker with 4dKH solution.

Check out Clive's excellent article - http://www.ukaps.org/drop-checker.htm

My advice it spend the £200+ on something else.


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## Antipofish (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*



			
				George Farmer said:
			
		

> pH controllers are widely regarded amongst many planted tank enthusiasts as a waste of money and may actually do more harm than good.......



Thanks George, that was exactly what I wanted to get to the bottom of   And it was as I thought could be the case.  More important for the salties I expect.  I have a dropchecker on order so if its a nice enough bit of kit I will get an extra one too so I can measure CO2 levels in different parts of the tank.


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## GillesF (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*

I totally agree with george. You're beter of spending your money on a good co2 setup


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## Radik (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*

PH controller is good if you have inert substrate then you can probably control Co2 fairly well.. But as said above you need to know what is your KH and that KH remains stable. 

In substrates which are altering water PH such amazonia they are completely useless.

What you can do as what I did and worked well I have controller but I am just using PH probe to watch rise and fall of PH when Co2 is on an off. It is instant Co2 detector unlike any drop checker and from the table above you can read when your PH stabilize and maintain desirable co2 level. 

You do not need controller for this really once you inject co2 and watch it you will notice that there limit to how much co2 you can inject vs how you open your needle valve. Few tunings and you get pretty stable co2 rate. Drop checker is behind almost 2-3 hours.

Also it was interesting to see in Amazonia tank without Co2 how PH fluctuates during day/night..+-0.3 there was still some co2 from the atmosphere and PH went down during night and up during the day.

In co2 injected tank you can also notice after 3-4 hours of photo period that your PH is going up as plants increase co2 uptake. 

So if you want something buy some digital PH monitor.. not PH pen.. with good probe which cost half of the controller.


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## foxfish (22 Feb 2012)

*Re: pH Controllers...how to maintain a CO2 level AND pH leve*

Love my ph meter viewtopic.php?f=21&t=19952


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