Hi all.

I had bought the ADA Drop Checker. Apparently, it is using pH value to gauge the CO2 level within the aquarium.

Funny thing is, the instruction given was to add a drop of the ADA pH reagent and fill the checker ball is half-full with aquarium water.
Initially, I had assumed that it is working because it seems to be within the color range of Yellowish Green. I turned off my CO2 output and it is still at that color range

Shouldn't it have turned back to blue?
Anyone able to help?