Cannabis plants need CO2 as part of the process of making energy from light via photosynthesis. Using CO2 in an indoor garden will result in about a 20% higher yield. Although, you may not want to give your plant CO2 throughout the entire grow cycle...
Grateful Grower, a grower on YouTube, has an indoor garden where his plants are currently on week 5 of flower - day 33 to be exact. He transplanted them into 1-gallon grow pots and is using Pro Mix as his growing medium. He used CO2 for this grow, however, he didn't use it for the entire grow.
He only uses CO2 in the vegetation stage for the first 21 days. Why? Well, he talks a little bit about that in his video below. He also talks about the highest yield he has gotten from using CO2 vs not using CO2. His results may surprise you...
Check out his video here:
Products shown/mentioned in this video:
Helios 7- http://amzn.to/2jIVx6w
Lumatek ballast- http://amzn.to/2jJ1LDt
Dominator XXXL 6" grow light reflector- http://amzn.to/2jIRoiR
Hortilux 1000w HPS blub- http://amzn.to/2kcbcfA
Vortex 8" inline fan- http://amzn.to/2jIPMpd
Carbon filter 8"- http://amzn.to/2jyYcgN
Temperature and humidity monitor- http://amzn.to/2gcqiyY
Oscillating fan- http://amzn.to/2eIaG4X
Advanced nutrients- http://amzn.to/2jof3EE
Tomato cages- http://amzn.to/2l5S1QT
Plastic grow pots- http://amzn.to/2jLTz1o
SCROG net- http://amzn.to/2iVzzZF
Pro Mix- http://amzn.to/2ljAwNq
Click here for other equipment that I recommend