I can't speak to physiological changes, but I've never seen any
negative impact aside from slower growth result from less CO2. At
concentrations under 20ppm, CO2 is like a speed control: lower the
bubble rate, plant growth slows down. Increase it, plant growth
accelerates.

That's good to hear. I was worried that using CO2 might be a bad idea if the
plants are to be later transferred to a tank without injected CO2. If moving
them to a standard tank just means they go back to their normal growth rate,
then there's no problem. Thank you for taking the time to reply.

Francois