Philippe wrote: > Where does the 3ppm concentration of CO2 in the bucket come from ? From the air. > Does it depend of temperature ? I think so, but it doesn't vary too much at the normal aquarium temps. I usually see 3 to 4ppm for non-injected water. -- Chuck Gadd Director of Software Development, Cyber FX Communications e-mail:cgadd at cfxc_com http://www.cfxc.com