But why a soft coral in the refugium vs. anything else?
Simply because I have so much of it. I peel it off my back glass, glue it to some rubble, put in in the sump to grow a little more and trade it at my LFS
for store credit. Then I peel more off the back glass, make more frags, trade it and on and on and on.
You can probably use whatever algae type you want in your sump, but chaeto grows extremely fast (your not actually exporting the nutrients until you remove the algae from your system) and it doesn't need lots of light. It's simple and effective.