"There are three different fish which are known as Grouper in the US market; the Red Grouper, (True) Black Grouper, and Gag which the market commonly calls Black Grouper. True Black Grouper is hard to come by. Both True Black Grouper and Gag have a higher yield and firmer texture than Red Grouper."
Source: Chef’s Resources
Black Grouper that is caught in the USA South Atlantic Ocean or Gulf of Mexico is considered "Good Alternative"
Grouper skin is very tough and bitter. Most chefs decide to remove the skin prior to cooking. The firm meat has a mild and sweet flavor. It is also a very versatile fish that can be grilled, baked, broiled, or deep fried.