dunno.. but in my 3 tanks... all 3 have great plant growth..
1 has no air pump and the water level touches the power filter, reflected sunlight durring the day
1 has an under gravel air pump tube thing, powerhead with slight bubbles, and the water level is about an inch below the power filter, reflected sunlight durring the day
1 (temp tank) is a plastic tub with the water 3 inches below the power filter, only a kitchen light, i have no idea how plants grow well in this tank but they do...