Folks also consistently underestimate the significance of seeing their chaeto stop growing. It's fantastic at grabbing and holding nutrients, so if it stops growing that means your whole tank is most probably nutrient limited.
Bacteria vs algae is the magic scenario we hope for when we carbon dose our tanks – that bacteria will "automagically" make the algae go away. We see here that in some cases it does work out. But as we see next, a "balanced system" promotes all three lifeforms.
This is the first time I've heard of selenium (Se) as a potentially limiting element. Lots of other interesting info in there about how the nutrients released are ultimately consumed and recycled either by other phytoplankton or bacteria.