Our established plant tanks have the best survival rate of all.
doesn't suprise me
Do you think it's because of the lack of NO2, NH4??
As for the co2/o2 issue...It's been my experience that if you aren't injecting co2 then the surface turbulence is actually a good thing -- for fish and plants the same. The fish definitely like it better, and as long as it's consistent then the plants will adapt as well. I typically have air bubblers on 24/7 in non-co2 tanks.
I've thought about it this way: CO2 is at a concentration in the air of 330 ppm. We strive in high tech injected tanks to achieve even 30ppm, which is pretty tough. It's a given fact that surface turbulence and air bubblers increase the transfer of gas from
the water to
the air...loss of co2...and also from
the air to
the water -- typically gain of o2.
I would argue that the water can actually gain co2 from the air.
Whatever co2 it might lose very well may be gained back, due to the fact that air itself has 330ppm co2 in the first place! Keep in mind, I've got absolutely zero evidence to prove this.
It just seems to me that the amount of co2 generated from fish respiration is probably so tiny that the water could pull the same amount back from the air.
In the end, the more o2 for the fish, the better.