yeah, I guess covering the tank is not a bad ideia...

I prefer the acid method. In my nano (40 liters) it lasts longer, is easier to adjust and does not leak into the tank.

Of course it is a little more expensive (but not really expensive - maybe 4$ a month) and has the risk of exploding (highly unlikely). Manipulating the acid isn't a real problem.

I have read your suggestion of pluging the power head to the timer in other thread, but it doen'st work here. The PH get filled with CO2 and has trouble starting in the morning. I would need a different design in order to keep the CO2 out of it. Or a new pump that has no problem in starting when filled with air.

Regards,
Bode.