Anglers and Frogfish are ambush predators and can eat almost anything small enough to fit into their (very large) mouths. This can include other fish as well as inverts like crabs, shrimp and others. Use caution when choosing tankmates. These fish are not very active and can be kept in a fairly small tank (depending on species) and can be kept alone as a "species-only" showcase.
They will typically eat almost any meaty foods offered but may only accept live items at first. Though they should be weaned onto frozen at some point, live ghost shrimp, mollies, guppies and similar items can be used at first. Eventually, they can be trained to accept frozen clam, squid, shrimp, krill and similar items. It is not unusual for these fish to fast the first few days to even weeks once introduced to a new environment or after a particularly large feeding.