The sargassum fish is a voracious ambush predator that is also a cannibal. One individual was dissected and found to have 16 juveniles in its stomach. It stalks its prey among the tangled weeds, relying on its cryptic camouflage for concealment. It can clamber through and cling to the seaweed stalks with its prehensile pectoral fins. It dangles its esca as a fishing lure to attract small fish, shrimp, and other invertebrates. It is able to dart forward to grab its prey by expelling water forcibly through its gill openings. It can expand its mouth to many times its original size in a fraction of a second, drawing prey in via suction, and can swallow prey larger than itself.