DIY CO2 Kit — 2-Bottle Yeast System

The two-bottle DIY yeast CO2 system improves on the single-bottle design by staggering the refresh schedule between the two bottles, so as one mixture nears exhaustion the other is still producing CO2 strongly. This dramatically reduces the output interruptions common with single-bottle yeast systems and provides a more consistent CO2 supply for planted aquariums. The kit includes dual pressure bottle caps, airline tubing, a bubble counter, a check valve, and a ceramic diffuser — all the components needed to assemble and run the system immediately. The two-bottle design also increases total CO2 output, making it practical for medium planted tanks up to 100 litres. An excellent intermediate step between a single-bottle beginner kit and a full pressurised CO2 system.