This is the one I am using. http://www.aquariumplants.com/Aqua_Medic_CO2_Continuous_Test_p/am71539.htm
I have the sucking cup facing the top and with the container hanging down. I am using a 4dkh solution purchased from [Ebay Link Removed] I am also using the ph solution from the API kit. The drop checker has been in the tank for 2 hours. The color is still blue.
I have the sucking cup facing the top and with the container hanging down. I am using a 4dkh solution purchased from [Ebay Link Removed] I am also using the ph solution from the API kit. The drop checker has been in the tank for 2 hours. The color is still blue.