My zoas don't seem to care about food at all. The only ones that like it are the larger Palys like the Implosions. Personally in a Zoa/BTA tank I wouldn't waste water quality by feeding the coral. The zoas absorb nutrients/amino acids out of the water column but don't really eat a whole lot. Unless you are actively trying to make a BTA grow quickly you never need to feed them either provided you have sufficient lighting and they aren't already bleached out.
If you have LPS/SPS you can play around with it and of course feed any NPS. Also keep in mind that any food you feed your fish (and the poop that comes from it) dissolves which provides sufficient protein/nutrients to the zoas. Quality frozen foods like Rod's food also contain plenty of coral food in them.