The "not an apex predator" bit is correct - from old catch data and more recent stomach content analyses, goliath grouper primarily feed on smaller slow-moving benthic animals such as burrfish and crabs. If I recall, in the more recent gut content analyses other snappers and groupers made up less than 3% of what was found, and the old-timers who used to spearfish for them could never recall finding any (although they did find spots with goliaths were also abundant with snappers, groupers, snook, etc.). It takes more than size to make an "apex predator;" the term defines a predator feeding at upper trophic levels (e.g., bull sharks or great hammerheads feeding on blacktips).