Alright the cool way

to test C02 is with a drop checker. It has some mixture that goes into it that measures out to 4 on the KH scale. It measures C02 by the 30ppm standard and turns a nice green color when you are near the mark. Yellow is to high and blue (the usual at rest color) is low.
You place the drop checker in the tank. Wait about 3 to 4 hours for your reading and it'll last about a month or so before the solution needs to be changed out.
Now being that you are using a known KH value your readings are more precise than with the KH and PH method. Plus it runs all the time so you don't have to test as often.
