Matt has done a great job with this fish, however, I've found that if you don't approach keeping them HIS way, well, you can imagine how some folks are.
FWIW, we started our fish on browned-out acros (we had a good source for them on the cheap) just to get something into the fish. To get them eating prepared foods, is the key, and the hard part.
We took several pieces of dead coral skeleton and smeared different foods into them, placed them in the fridge briefly to let it "set" a bit, then placed whatever we decided to try into the tank with the OSFF. THEN, so as not to disturb the fish, Renee would hide under the blankets and peek out to see if there was any interest (their QT/weaning tank was in our bedroom at the time). Each "peck" was a small victory.
Once you find foods the fish will accept, the next step is getting them to eat from the water column. Once you get some weight on them, they're pretty darned hardy, altho if they go off their feed, a water change generally remedies this.
Many peeps have good luck with various roe and/or Nutramar Ova, but neither of our fish care for it. The tiny NLS pellets are a good food, as is shaved salmon flesh, mysis, and BS+. The more types of food you feed out, the better IMHO. The also enjoy hunting live pods (we keep live macro in the tank so they will breed). This fish requires lots of food, so multiple feedings are best.
Weaning this species "from scratch" isn't easy, in fact, I've never seen Renee work so hard at it.
HTH some.