Yes, a cube is already included. You don't necessarily need it if you change the water every day. Otherwise I would use it, as it inhibits bacterial growth. The cube must be replaced after one year.

I can only agree with that. However, I would like to add that I recommend the casts. Because let's be honest, who changes the water every day? If you have to spend a few francs after 12 months, that's within reason. Otherwise, I would ask myself why one spends so much money on the whole device.