I've had good results with Reef Roids. Bought it at Aquatek. I use it with a small baster. Be sure to turn your pumps off while you target feed and be careful not to overfeed. Once or twice a week does the trick for me. This is supplemental feeding, since zoas, mushrooms etc get most of their fuel from photosynthetic zooxanthalae. But like you, I'm curious what other people are using as well. I think phytoplankton is good too but I have a hard time keeping it fresh for any long period of time unless I were to cultivate it myself.
http://www.polyplab.com/reefroids.html