CO2 generators (these are normally natural gas powered and range in price from $250-500 depending on output and quality)

Tank CO2 injection systems (pretty pricey but very effective)

Homemade CO2-mix 3/4 cup of sugar, 6 cups of cold water and 1 teaspoon of yeast

__________________
Blow the chronic smoke in the air then mix the hash with it

hey purplegorillas; how long does that homemade co2 mix last? is that a daily thing?

hey 1134206, that co2 mix should last you about 2 weeks

__________________
There's Gonna Be Alot Of Slow Singin
And Flower Bringin
If My Burgular Alarm Starts Ringin

there's no way that last 2 weeks. 2 days or 3, tops. i use a 2 liter coke bottle (3/4 full), 1 cup of sugar and a teaspoon of yeast for 48 hours of CO2.

__________________
This proves my theory!

every time you sake it (if it bubbles) you are making more co2

__________________
CHECK OUT MY DIY 150 HPS SCROG GROW
http://www.rollitup.org/grow-journal...w-coments.html

Yeah I use a white milk jug. 1tsp yeast+3cups sugar+ 5cups water //can take a while for it to really start working. 24-48. works right away but produces more once reaction in full swing.
I cut a hole in the cap and placed a flexi straw (short side in hole) in it.
I point the straw down to the base of the plants and the co2 rises.
It does seem to raise temp though in a confined space.

You cannot beat the great outdoors, unless you have a greenhouse... a big greenhouse.

Else, there's aero. Difficult to manage as the spray nozzles have a tendency to get blocked up. Which is fine so long as you keep on top of things... if you don't you can lose an entire crop within hours.

Next in line, I believe, is NFT... although with the accelerated growth rate (i have heard of growth in the range of 7 inches in a day, not unusual to get 5") often when your plants encounter problems it can be too late for you to do much about it.

Next, would be DWC... easy to maintain and excellent growth rates in veg' of 1-2" a day. It could be more, as this is my own experience... I'm fairly new to it but I can tell you cannabis loves it.

Then, imo you have hydro... followed (some would say very closely) by soil.

I started in soil, then hydro and now dwc. In fact I have my last soil plant still in flower (an ex mother), likewise my last hydro grow is also in flower. now that I've grown dwc I feel that I've found the medium I'm most comfortable with.