From what I've read young Niger are OK. Blue jaws, pink tails, ringens (sargasum), and of course cross hatches are the most "reef safe" long term. I think most of what you read will agree the ringens is the mellowest.
... Just don't get attached to your snails, hermits, crabs and possibly ornamental shrimp.
That said, I think there's a pink tail in my future for my 375.