Niger isn't as aggressive, yes! But it depends on you to trust the fish or not with your corals and live stock. Each individual fish is different just like people. For an example, a Yellow Tang is considered reef safe, but I have heard many bad stories about how they ate their Zoos and other corals. While some fish may do something like this, it doesn't mean all of'em will. I had a Niger once, very calm fish and very shy, rarely to be seen. It just died one day for no apparent reason while the other fish is just fine. Very nice fish I do have to say. It never bothered my Hermit Crabs either. I then replaced it with a Humu Humu Trigger, very shy as well and didn't last, died within 3 days cause he wouldn't eat. Everything else was fine, I got another one the following week and had it ever since. It was the BEST trigger I've ever own, very friendly. Gets along with my Yellow Tang better then the previous two triggers. It eats like a pig, unlike the previous one. The Yellow Tang and the Humu Humu sleeps together at times, feed together and swim together. It's quite cute!!! I've had'em together for over 7 months now. The Humu Humu doesn't bother my hermit either, but he will nip at the fake coral within the tank and have taken chunks off of it, I would NOT trust this trigger with corals. She comes to the front of the tank to say hi every morning and everytime when I feed or walk into the room. We named her "Dolly". We're upgrading her tank sometime soon, it would be just her and a Heniochus Butterfly. The Yellow Tang is moving into our new 90g Bowfront reef tank. :happyfish