Confused about PH KH & CO2 - The Planted Tank Forum
 
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post #1 of 3 (permalink) Old 08-17-2017, 11:42 PM Thread Starter
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Confused about PH KH & CO2

From the information I read on the Internet, PH & KH can be used an indicator of CO2 level, if for example my KH is at 4 and PH at 6.6 it would seem from the charts that my CO2 would be at 23.9. Does it mean my water contains CO2 even though I have not added any?

If this is not true which I suspect it is not, this would mean that before adding CO2 I should either lower the KH or raise the PH otherwise I will most likely run the parameters into the red zone and stress out the fish, does this hold true in practice?

These are probably a dumb questions, but I am trying to figure out how to best setup my new 60 gallon tank. I have been keeping planted aquariums for around 20 years with much sheer luck, I figured early on that if I have plenty of light, add CO2 using a PH controller, lots of plants and enough fish I would be home free and it seems that this approach has worked, but with all the information out here it seems that it is not the best way to fly.

I will greatly appreciate your feedback.

Mike.
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post #2 of 3 (permalink) Old 08-18-2017, 01:18 AM
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Personally I would not worry about kH at all.
Aim for a drop in pH of 1. You can turn your CO2 off at night if you have a solenoid. The change in pH should be well tolerated by your fish. I say "should". You need to keep a close eye on them when titrating the CO2 delivery.

You can start adding CO2 slowly, when you are home and will be home for a while. If fish start gasping at the surface or acting lethargic you need to slow down the CO2 delivery. Adding a bit of surface agitation should help as well.

If you are worried about your fish when you are starting out, as most of us are, you can begin by starting with lower amounts of CO2. The best way to do that safely, without ending up with an algae mess, is to use less light.

Last edited by jart; 08-19-2017 at 02:19 AM. Reason: Changed "controller" to "solenoid".
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post #3 of 3 (permalink) Old 08-19-2017, 02:16 AM
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Quote:
Originally Posted by acmeseed View Post
From the information I read on the Internet, PH & KH can be used an indicator of CO2 level, if for example my KH is at 4 and PH at 6.6 it would seem from the charts that my CO2 would be at 23.9. Does it mean my water contains CO2 even though I have not added any?

If this is not true which I suspect it is not, this would mean that before adding CO2 I should either lower the KH or raise the PH otherwise I will most likely run the parameters into the red zone and stress out the fish, does this hold true in practice?
You are right in your thinking. There are many things dissolved in your tank's water that can affect pH other than CO2. So if you had parameters as you mention above, you are right, unless you were adding CO2 then you would not have 23.9ppm CO2. Even if you were adding CO2, again since other things in water affect pH, the 23.9 would be just a rough estimate. The pH/KH table is an estimate of CO2. You can use it to help you figure out what to do with your CO2 injection. The method the poster above mentions works great as well.
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