A friend of mine had a huge HA outbreak. I turned his lights off (he was away) for a week. Had Kalk dripping slowly into the tank. After 2 days you could see the HA was dying back, at this time the skimmer (Aquamedic SL 1000) was pulling out dark gunk. After one week put the lights back on. Almost no HA and the water was very clean.
The author claims "good results" and "purification." What are the results? The classic "my tank has never looked better!" Well, if your tank has been in the dark, and you turn the lights on of course it looks great. When I go away for a weekend and come back, I (hopefully, barring any events) think the same thing...wow, the tank looks great! I can think of no "purifying" actions this would have of any meaningful consequence even in theory.
I can perhaps understand that a drop in primary production could lead to a reduction of fast reproducing species (like diatoms listed), or maybe in tanks with water column blooms, but as Chuck said, this is a potentially dangerous thing to combat, especially if the organsisms produced toxins. I even wonder how the author knows they had dinoflagellates. But what are the "purifications" taking place? None measured or listed. No experimental method. Just another "I did this and the tank water is clear and the polyps opened up." That this is a skimmerless tank may make some difference in the perception, and that there appears to only be a single tank here and not multiples where function based compartments can be established, and perhaps heterotrophs process some waste without as much production taking place, but there are other ways to theoretically accomplish this. Long and short of it is that this is a notion with an observation and a sample size of 1. It is not a method with results, not even qualifiable results.