In an earlier post you had said that you had found a drop checker on ebay, do you what type or brand it was?
And I don't wish to be rude in any manner, how long have you had this experiment going on?
After reading and following your posts on the drop checker did you test all of the levels simultaneously in seperate tanks or were adjustments made to the same tank over time? How did you compare colors or was it a judgement call, or did you take pictures?
I am very interested in tracking/mointoring CO2 content but I have doubts about most of the methods out there. Can one just decide if there is enough CO2 in the tank by the appearance of it's inhabitants(fish /plants/algae)?