Thanks people, straight forward and I understand what your saying! (; I just have this feeling that changing tubes, refilling mesk etc wont work in the long run for me, I need passive systems since I tire pretty easily. Also Im on a tight budget.
About 2 days after I filled the tank with water I had small bubbles rising and sticking to the leafs - excess CO2 escaping?
Just a second though - what if one had a sump in which one put dead matter, and have the outflow constantly disturb the soil and add circilation as an oxygen suply?
It would need a thin sponge on the intake of the pump which brings the water back to the tank - will the CO2 follow the water back up or just evaporate above the sump?