I doubt it was your electrig hermits. They are Calcinus Elegans, the electric oranges are endimic to Hawaii, the electric blues are endimic to the Marshal Islands. They are primarily herbivores and have been reported to even eat hair algae. They can get large, but have a rather short lifespan of about 2 years. I have never seen or heard of one attacking a fish, but, you know how it goes, if a crab has an opportunity, don't think it won't take it, it may, or it may not. All crabs are opportunistic, no matter how reef safe they are, however, I think this is an excellent reef tank species (even if they do knock over a frag here and there.
If you don't wan't them, I will takem off your hands!
"Maybe in order to understand mankind, we have to look at the word itself: "Mankind". Basically, it's made up of two separate words - "mank" and "ind". What do these words mean ? It's a mystery, and that's why so is mankind." ~ Jack Handey