They like tiny coral foods one or two times a week. I'd use something like reef roids or reef chili, a zoo/phyto plankton mix, or any of the reef snow types of foods. I used to feed mine reef snow broadcasted across the entire tank, not necessarily blasted at the goni itself. It responded well to that but the downfall of the coral for me was my clowns trying to host it, they were irritating it too much and it went downhill to the point it just died. I'd be careful with a goni if you have clowns without an anemone.
How hardy are these corals assuming they are fed well? Is coral frenzy a good food for them?
Some folks have really good luck with them and others do not, its sort of hit or miss. They do better in "dirtier" tanks that aren't ultra-low nutrient. Coral frenzy may be too big for them. In the wild they capture plankton and other micro morsels of food through tidal movement, so they like a little flow too, not a ton, but just enough to keep their tentacles moving in the water.
I might just buy some reef roids or some other smaller food if I keep one. I assume they need to be on the sandbed?
I kept mine on the sandbed but it was also in a 20 gallon, so there wasn't many places that weren't fully blasted with light to put it. I have a friend that keep his around the middle of his tank on a rock and I think it has actually encrusted onto the rock.
