I love my coral beauty, I'd debated between that and a flame angel, but I love the subtle, deep coloration on the CB.Coloration seems to vary a good bit between individual fishes. Mine is not at all aggressive towards tankmates, and is in fact, one of the most shy fish in my tank, it took a couple months for him to stop hiding when I approached the tank.I agree, either should do well in your 40gal, but do make certain to see it eat in the store first.