Blue Dot Argus Grouper (Cephalopholis argus)

Peacock Hind groupers can flip their whole body color from pale to almost black in seconds, a mood ring for stress and hunting mode that most keepers only notice once they know to look for it. Every grouper on this list uses the same trick to actually catch dinner: a mouth that expands so fast it creates a vacuum, sucking prey in whole rather than chasing it down. This one is still a juvenile-sized speckled charmer for now, but budget serious tank space for the 20-inch predator it's going to become.

Care level: Easy · Temperament: Predatory · Max size: ~20"+ · Min tank: 180+ gal (adult) · Diet: Carnivore, live/frozen meaty foods