Ok.. Here is how to refill. You need a larger canister of CO2, and a fitting that adapts it to airline tubing size. When one Fluval CO2 cartridge is empty, connect one end of some air line tubing into the valve that the Fluval kit comes with. Make sure it is connected securely. Also open the Fluval CO2 valve all the way. Then, connect the other end of the tubing to the larger CO2 tank, and slowly open the valve/fitting. After a while the Fluval canister should be filled, and then you can close the valves of both CO2 tanks. I hope that was understandable. Lol
I have not personally done this yet, but I am quite confident that it works.
I have not personally done this yet, but I am quite confident that it works.