LOL! Go ahead and sing to them girls, especially if you have a voice!

Rusty is right tho, exercising in the grow room will make you and the girls healthier, I just can't/won't exercise in a 4'x6' closet full of plants as there is not enough room...singing is my preferred way and everybody will tell you I can't sing a lick! However, the girls seem to love it, so why not? (they do not like my rockin' guitar playing nearly so much as my singing, although they did dance around a little...maybe should not have used the Marshall 100 amp?) Just sitting in the room and breathing is better than nothing. I will agree to disagree with Rusty about levels of co2 a cannabis plant can use...300PPM co2 is ok, but 1500 to 2000PPM co2 is better IMHO....with the caveat that you must first have all the other basics down pat.

One big problem with using dry ice or compressed co2 is the expense, $2/lb/day for weeks or months(and daily trips [hmm, very suspicious?] to the ice plant or you will have the dry ice storage problem), and the other methods can be messy and stinky. You can pick up a 20lb co2 tank and regulator for a couple hundred bucks online or at your local welding supply store also. You can set up a propane or natural gas burner if your not afraid of fire and have no heat retention issues. You can sing, breath, and exercise for free. Free, I like!

Another problem is control...unless you have an accurate co2 sensor/monitor and an accurate dispensing system, how will you know if your exceeding 2000PPM? Or just spending a lot of money, or making a big stinky mess, to get only 320PPM? Control and monitoring devices can be very expensive. 3000+PPM can be deadly to you and the girls. I seriously doubt I can generate 3000PPM by singing, so singing seems fairly simple and safe to me, compared to generators, chemicals, bottles and regulators.

A theory on co2 and plant use is that in the early days of plants (possibly many millions of years ago) there was more co2 in the atmosphere than now and some plants still have the leftover genetic (?) capacity to use more co2 for growing than actually exists in the atmosphere today. Having used co2 and not used co2 in all forms in the past, and having a relatively small area to worry about now, I choose singing to those happy girls as the most cost effective way to improve my crop. Does it work? It works for me.