The Best Ways to Produce CO2 for Indoor Gardens
There are two good choices for efficiently increasing the CO2 levels inside your garden. The first method is to use a CO2 generator. The second option is to use tanks of compressed CO2.
Generators are more convenient because they hook up directly to your natural gas line or propane tank, eliminating the need to periodically fill your CO2 tanks. The drawback is that they produce extra heat as well as CO2. Most of the heat can be ducted away, but can sometimes still cause a problem for plant growth.
I prefer the first option, which is to use a CO2 generator for the production of CO2.