Hi,

I think the airstone is to create a current to prevent it going stagnant? But your probably right about the waterfall as I can't think of any other way to fill it in the first place.

The reason it stays full of water is simply the air pressure on the surface of the water in the open section as far as I know.

I might try and find out how it works later if my evening turns out as boring as I wish.


dr del