I feed mine mostly with... NP Biopellets.
No seriously, using NPBP for over a year and all my SPS's been showing incredible PE even during the day, I'm pretty sure my tank is filled with bacteria growing from the NPBP and that's what my corals' been feeding on.
I even have a small frag of leather coral growing on the bottom of a piece of live rock, that was left behind when I removed the mother colony. It received absolutely NO light and it's still thriving and growing steadily. It's sustained by feeding on the bacteria alone.
There's also a thin film of bacteria on top of the water inside my overflow chamber, that I had to manually remove every couple of days. I've hardly feed them with anything else now, except a little Reefpearls once every 2 weeks.