Really I see it as if they are a long skiny fish it's going to be a snack, if it's a small fish but has a larger round body is ok. Do example a 2.5" tang will be fine but a 2.5" chromis will be a snack. They are really bad eye sight and need fish that arnt afraid to flair up and get in the snowflakes face. For example when I feed my tank my snowflake comes out and wants to bite every fish because he thinks it's food. My sailfin that's about 4" puts his fins up, turns his profile to the eel and backs rights into it to show it he's to big and means business. It's amazing how blind they are, they can't see anything and you will see what I mean as soon as you get one. Mistaken identity is the lead cause of death from snowflakes. I don't think they want to eat a fish ever but they just can't tell the difference and when they attack they are extremely aggressive.
My stock list:
12" snowfake (they grow really fast mine was 8-9" 2 months ago)