I had one over 20 years ago.
Very agressive , a swimming vaccum cleaner , keep it only with the toughest fish that can compete with him for food, otherwise you'll have to stuff your blue Grouper till it will look like a balloon (and it will) and then let the other fish food.
I had to give my grouper back to the shop as it just kept on growing, I remember, as soon as they acclimated it in their show tank, somebody came in and decided to buy it.