FishProfiles.com Message Forums

Are CO2 levels directly related to PH? For instance, if my PH is at 7.5, does that mean that my CO2 levels are lower than if my PH was at 6.5? And is this an safe way to monitor CO2 levels in my tank?

The ability of your water to absorb CO2 is related to pH and KH. If you measure your pH and your KH then take the values and go to http://www.fishprofiles.com, then you determine the level of your CO2 absorption in your aquarium.

Let's say that your pH is 7.0 and your KH is 4dGH then you have 11.8 mg/L of CO2 is your system. If you then inject CO2 and your pH declines to 6.6, then your CO2 has risen to 30.0 mg/L.



__________
"To steal ideas from one person is plagiarism; to steal from many is research."
researched from Steven Wright

http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm Not sure if this is the exact link you were looking for but it will do.
KH is a measure of your waters ability to absorb acids ie hydrogen. Overall the higher the kh the higher the ph but if you add co2 the ph will drop without the kh going down. A lower ph compared to kh is mostly caused by co2 addition. That allows you to measure the amount of co2 in your tank. You can't measure co2 on ph alone because it is affected by many other things.

Last edited by sham at 06-May-2005 13:48

And just to make things clearer: increasing CO2 levels will lower the pH, but decreasing pH levels doesn't mean that your CO2 levels will increase. Unless you decrease pH by adding CO2, of course.

This is all great info, thanks. Is there any indicator which will tell me if my CO2 is out of control? for instance will my PH spike or drop?

I guess I am just being lazy and should get a CO2 gage...

Hi,
As was mentioned in an earlier post, you only need be
concerned if you are deliberately injecting CO2 into the
tank for the benefit of plants.
If you find your fish all gasping at the surface in the
morning, when the lights come on, then you have too much
CO2 in the tank and would need to add an airstone or adjust
the filter return to rile the surface of the water.

Frank


Last edited by FRANK at 06-May-2005 15:09

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

While the CO2 level is affected by more than just the kH and pH, if you follow a few simple rules, you probably don't need to test the CO2.

1. Don't use a lot of chemicals in your tank, especially any "pH down" or "pH balance" products. The chart that Bob mentioned above will work beautifully if your water is chemical free. And most CO2 test kits will say somewhere in the fine print that these chemicals can screw up their results, too.

2. Monitor your pH at the same time every day. You should expect a little bit of swing in your pH each day as any plants start and stop their photosynthesis. By checking at the same time every day, you'll see only long term changes, and not daily ones.

3. Make sure that your kH is at minimum 100 ppm. kH is like a sponge that can soak up things that try to change your pH - having at least this much kH will minimize both the daily and long term pH swings.

4. Watch your fish and plants. They'll let you know if anything is getting out of whack!

Have fun!