Yea, they can get pretty big and the majority who have very large Nigers state they are mean
Sargassum's even when fully grown should be a good fit for a 125g, they arent mean or hyper.... Blue jaw would also work......
I have been debating on adding a Niger to my tank, I want more then one trigger and I was hoping a sargassum and black trigger (my favorite trigger) would work which didn't. Just saw Nigers on sale for $11 thus debating if I should give one a try..... Few other things caught my eye as well..... Thinking of attempting to catch my Sohal and put him in "time out" for a few months while I add new fish.