Lionfish

Lionfish are a large, generally peaceful family of fish. Their dorsal fins contain spikes that are used to inject venom into attackers as a form of defense. They are not really aggressive towards other medium or large fish but will swallow whole any fish or invertebrate that's small enough for them to eat.

Preferring to stay hidden when possible, Lionfish are best kept in an aquarium with plenty of caves for them to retreat to.