[Delphinus]

Unfortunately I only have first hand experience with the CBB.

I haven't been able to find much info on the longnose, other than it's supposed to be easygoing and readily accepting of prepared foods. I guess what I mean is, I haven't really found much useful info in how "safe" it is with clams specifically. (Would love to know if it's OK or not, but I really am not going to be the one to sacrifice my clams to the cause of finding out!)

Most of the fish you listed are reputed to be fairly dicey in terms of reef-safeness... I'm not sure I've heard of many instances of them in SPS tanks. Again, sorry, no first hand experience though.

One butterfly fish that is reputed to be a pretty good reef citizen is the pyramid butterfly, Hemitauricthys polylepis. IMO, that one might be worth checking into.