How to measure CO2 levels in tank?

[cgcaver]

I finally got my pressurized CO2 tank setup and going. I know you want to aim for a certain bubble per minute ratio to give you a certain amount of CO2 in your water. How do you measure CO2 in your water so you know how many bubbles per minute to run?

 

[czcz]

If there are no other buffers you can measure kH and pH and derive CO2. Great site including chart: http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm and calculator: http://www.csd.net/~cgadd/aqua/art_plant_aquacalc.htm

 

[cgcaver]

How many bubbles per minute do you guys think would get me close to normal ppm for a 55g? I know there are MANY determining factors which you have to take into account, but Im just curious about where to start while trying to get an optimal level set.

Also, why does my bubble counter slow down over time? When I set it at night, Im lucky if it's still putting out half that when I check it in the morning. This is really frustrating. Something in the regulator seems to be choking down on the gas getting through over time. My tank PSI is still going strong of course. Do I need to close my regulator valve down more? Thats really all I can think of...

 

[greenmaji]

The bubbles per min is not a very accurate way of measuring CO2.. It really depends
on how tight your total system keeps the CO2.. ie trickle filter or surface agitation on
the surface of the tank would require more bubbles than a canister filter and no surface
agitation.. Testing your PH and KH are more accurate as far as giving you a place to
start.
HTH