Is the threadfin butterflyfish reef safe?

The fact that it's hit or miss means it's not 100% reef safe. They can turn at any time if they get so much as a bit hungry, which means even if it's not picking at corals for the first few months, there's no guarantee it will stay reef safe the entire time it's in your tank.

There's another butterfly that would fall in to that category, but the name is eluding me.

 

yes, threadfins will eat corals.

However, there are 100% reef safe angels. There are several species of genicanthus angels- which are planktivores unlike most angels.

The name of the 100% reef safe butterfly is the pyramid butterfly. These are planktivores also, and feed on food in the water column, not off of the rocks.