Now add some plants, some water, some canopy over time and space.
Inverse square law is pretty much what we'd predict to find.

However, in the real world, it deviates.
So measure that afterwards once you are done here.

Measure, mark and follow a single leaf through a week or two, or a set of leaves(say 11 at random points in the tank). Plants will also adapt readily to light SFD as well as PAR and also through time/space.

Measure the effects of pruning weekly vs every 3 weeks.
Measure the effects of a MH vs a FL tube, spacing in FL tubes(say a narrow band with two bulbs near each other vs 15" apart).

As you can quickly see, you have an infinite set of possible questions to ask and test for there, and with respect to each plant species available (300-400).