It sounds like you read some really wacky info there.
The word "refugium" is taken from "refuge". It's a place, free of predation, where valuable pods
and algae can grow. The pods
feed the tank. The algae absorbs nutrients.
Diatoms will only grow if there are enough silicates to sustain them. If you have an abundance of silicates in your system, diatoms will grow everywhere, not just in the refugium. Refugiums do not produce silica.
Here is some information about silica.
You definitely do not want anything in the refugium that eats anything. That defeats the entire purpose of the "refuge". It doesn't matter if cyano
, diatoms, or nuisance algae grow in the refugium.
I don't keep my refugium light on 24/7 because I want the pods
to have a night time. Ideally, I would want the refugium light to go on opposite the display, but at this point I can't run it that way, so it's on around the same time as the display.
The reason folks say to run the light 24/7 is so your caulerpa doesn't go sexual and release nutrients into the tank. If you aren't using caulerpa for nutrient export, it's pointless to run it 24/7.