At least a 2 Kg tank of CO2 - a good regulator / solenoid / bubble counter assembly - a timer - CO2 proof (polyurethane) tubing (not air line it will crack) a non-return valve near the tank (again CO2 proof) - a bubble checker - and the delivery system of choice (diffuser or reactor). A good place to start in Europe is
and in the US
A helpful video at
- more on his youtube channel
Don't get one of the ready made kits - you'll spend a fortune on CO2 - spend the money on decent kit up front.