Longfin Bannerfish?

So my Supplier/LFS has some longfin bannerfish and I really want one for my tank or possible two. Are they reef safe at all?
I've been doing some research and I understand that Heniochus acuminatus is not reef safe while Heniochus diphreutes is reef safe. I also understand that they are extremely difficult to differentiate between the two. So if I do get the H. acuminatus, in what way is it non-reef safe? Do they feed on hard or soft corals or do they feed on shrimp, crabs etc?

 

I don't know much, but I don't think they are not reef safe.