You can get small units like the CD-3 that is a single burner for about 300 bucks or less on eBay. They are worth the money if you are going to grow for many years. A good controller is recommended but not required.

A good controller can save you time and money and keep the guessing out of your room.
Zandor Reviewed by Zandor on . C02 Question??? Should you run your room fans through the process or have them turn off? What would be the rate of C02 during bloom? Do you run C02 during Veg? Have a C02 tank as my system. Rating: 5