holly crap dude a 20 lb tank should last a 10x10 room a month.plants can only take in so much.i would change your system to run 3 or 4 times a day intermitently and have you exhaust either hooked up to a timer to shut off for 10-15 min at a time,whal the co2 is running.also if you use a/c you need to buy a dehumidifier so if your biggest worry is co2 production i would switch to the 3 or 4 times a day method.good luck to yah