Plants will not be able to take advantage of added CO2 in small gardens it does help although with large numbers and very high lumens. If your using 1000 watts or more you can benefit from added CO2. I have used it off and on over the years in small cabinets and have seen absolutely no increase in yields and a decrease in my wallets weight, save your money and put it into quality nutes as well as as much light as you can get without overheating your ladies. GL