Quote Originally Posted by hatch
It would be easier to get some dry-ice, put it in a water bowl around the root's or just bottom of plant. once or twice light's on.

Keep left-over ICE in freezer. Or just get reg.@ tank? Later
CO2 is heavier than air and by placing your source at root level, you're not going to get any of the benefits. Also, dry ice does not keep well in a standard freezer as it requires either much cooler temperatures or pressure to keep.