These are one of the hardest angels to keep - but only for the first month or so. I had one for a LONG time, but lost him in a tank crash when we were out of town skiing a few years ago. This is my all-time favorite fish - and this one was a great one.
The big challenges are 1) parasites and 2) getting them to eat. As you noted, they eat almost exclusively sponges in the wild. Mine went 3 weeks without eating. Finally, one day - I swear hours away from starving to death - he decided to eat. He got bolder and bolder until he ate out of my hand. If that one is eating frozen food, I'd say you've got a good shot.
Remember, these are pretty big Atlantic angels. Not as big as Queens, but big. They need a tank of at least 100 gallons.
These guys are not particularly "reef safe" - better than some angels, but will likely pick on clams. They seem to pick on everything - just browsing, usually. But, mine LOVED zoas. I swear he was stoned on them...
Bill
215g FOWLR... and anemones, GSP, gorgonians... carp, that isn't FO!
"I killed my first SW Fish in 1971..."