Another puzzling factor is the clarity of the glass. When I've seen bottle gardens, they all develop a thick scum from minerals in condensation, algae, and bacterial plaques.

This is a great GREAT point.

It would be nice to hear an explanation.

Magnetic scrubbing brushes. They're commonly used in aquariums.

There is also, Cellular respiration in night within the plant itself, which release some CO2 in the atmosphere. So may be combined with CO2 released by Bacteria and Cellular respiration in plant, it can survive.