When I did a planted tank a looong time ago I was taught that any surface agitation was bad for a planted tank due to the fact that it helped in reducing Co2 which the plants need desperately in the water column.
Thanks for any insights into this.
You're correct. Oxygen is a plant waste product, so an environment high in oxygen wouldn't be good for your plants. However, I use lengths of plastic tubing attached to an air pump and I run the end of the tubing in the bottom of my tanks. The water movement from the large bubbles circulate the water, so nutrients pass through the plant roots. I believe the water movement helps plant growth.