I have a Nutrafin C02 unit, although it was only setup yesterday, I have yet to see if it is functioning properly, but my question is how long should this unit be on each day. I read somewhere (cannot remember doing too many searches) that these units should be disconnected at night or the gases will suffocate the fish is this true?, also I have read a few of the threads on this site that C02 will lowered PH levels an KH level what are the later and how do you test this? and if C02 units lower PH level could this affect live stock within the set up, I have just started a new setup and going through the cycling process so this is not a problem as yet.