Flame Angel's are actually quite easy to keep. If they survive in your tank over the first four weeks of introduction they pretty much will be with you for a while (provided it wasn't captured using cyanide).
I have had one for 6 months in a tank with a number of ocellaris clowns, damsels, tangs, urchins, crabs, snails and 55 lbs of LR. I would say that if you have a quality filter and some alage covered rock (whether LR or simply grown over) these fish do great.
I feed mine Formula One flake almost exclusively (and some algae in a clip twice a week) none of my fish like frozen or brine shrimp anymore.