Planted Tank Guru
Join Date: Nov 2005
Location: Saint Joseph, Illinois
You can't call it a "fact" unless you have proven it over and over again with controls and an indeprendent variable.
The observed reasoning behind pearling is just as Ian and LS6Tommy said. The water becomes saturated with oxygen during photosynthesis. No more can be dissolved, so oxygen production forms bubbles on the plan't surface. Water changes duplicate this since tapwater is often saturated with O2 as well.
Some tanks never pearl, some tanks pearl constantly. Pearling is not necessarily an apex of growth that plants reach.
In college....so no aquariums for a while.....