i agreeNot exactly correct. DIY co2 generators work very well for tanks up to around 40 gals. I have a 30, and 40 gal. on yeast generated co2, and they are doing excellent. I will concur they could be sporadic if your not diligent in keeping the generators renewed often.;-) I use a two bottle system on my tanks. They produce a consistent 1BPS. I make up a new bottle every 2-3 weeks.