You can try this webpage to see one man's journey, how he grew, and what he found. "Adventures with needle valves" 6 Bubbles a minute? No wonder I don't get this needle-valve thing. That doesn't sound like much CO2, even for a small tank. I range from 60 bubbles (29 gallon) to 240+ bubbles (180 gallon) a minute. Lyndle Schenck