DIY paintball

[Aleeeeeezy]

So, I'm completely new to fish keeping along with plants, but I have a 20 gal I'd like to begin to plant. I really don't have enough money for a CO2 commercial system (still in high school, no job) but I'd rather not deal with the inconsistencies of a yeast producer. I've been looking at the paintball tank method, but I read in one article that someone's tank exploded because of build up, or something? Also, I can't find one of the ASA On/Off Valves. So if anyone could link me to a regulator or something that would prevent explosions, and a link to a valve, I'd really appreciate it. Thank you!