lol it's the air! You are seeing what Derek420colorado's max O2 technique can do lmao.
But seriously you are doing a great job and yes you are correct your roots are going to fill that bucket completely they will look like this
View attachment 768381 when it's done. When you add enough air the rest of the plant is able to maximize the rest of the growth variables like light and proper temps.
And I think
@sanguine maybe did one. I can't remember but I think I remember seeing someone do one and DWC.