CO2 indicators

[Scuba Guy]

Does anyone use that CO2 indicator in which you put two drops of solution into a cup and invert the cup under tank water. Supposedly the color will change with the concentration of CO2.

I bought one and the color is blue (indicating not enough CO2) - which I can't believe. I inject a 'ton' of CO2 and my plants bubble Oxygen like crazy - I was worried I was adding too much CO2.

[Danny M]

Do you put 2 drops of solution and nothing more?
I don't knbow the kit you're using, but, I think, for most of the kits you have to put 2 drops of sol. in some water; this mix goes in your small glass or vial. Water with a known Kh. In fact, it's the same as a ph kit, but modifying the kh of the water in the test vial, you can change the concentration of co2 where you want the vial to change color.