My gas guyz co2 has made my aquarium plants turn into an absolute jungle. It lasted for ages, and the driver replacing my empty bottle for a full one was stealthier than Santa Claus. I placed an order after dinner, and the new bottle magically appeared exactly where the old bottle was at some indeterminate time early the next morning. I was genuinely amazed with how quick it was, and how quiet they must have been because there was not a single wood from my dogs, who usually go bananas when the postie comes!!