[2] The king angelfish is a non-migratory tropical fish that inhabits reefs in the eastern Pacific Ocean from the coast of Peru north to the Gulf of California, including offshore islands as far west as the Galapagos, generally at depth of 4–30 metres (13–98 ft).

[7][8] The biogeographical models from the study also show that the Tropical Eastern Pacific kingfish occurred before the Isthmus of Panama closed.

This suggests that the clade of Tropical Eastern Pacific kingfish may have originated from an Indian Ocean invasion after the closure of the Tethys Sea.

[12] However, the Conservation Regulation of Mexico granted the status of special protection to the king angelfish in 1996 due to overfishing, thus the harvest of this fish was limited and caused two fisheries in the Gulf of California to close in the early 2000s.

[13] King angelfish are diurnal and feed on sponges, other sessile invertebrates, zooplankton, and certain species of benthic microalgae.

H. passer spend the majority of time foraging in the middle of the water column feeding on zooplankton or in benthic communities grazing on algae.

[14] In the Mexican Pacific Ocean, king angelfish are vital spongivores and were observed to consume up to 23 out of 24 different species of sponge surveyed with a specific preference for the order Hadromerida.

[16] The digestive tract in angelfishes is fairly simple and is composed of a pyloric caeca attached to the stomach and an intestine connected to the terminal sac.

[18] The king angelfish also hosts gut protists in its rectum, Protoopalina pomacantha, an opalinid flagellate resides in the large hindgut chamber of the fish.

[19] The king angelfish is considered an ecosystem engineer because it grazes in benthic communities which creates habitat for other species.

[20] H. passer primarily inhabits the middle and bottom of the water column of rocky tropical reefs and can be commonly found in crevices of large rocks.

[2] H. passer is well-studied in the Gulf of California and is considered a dominant species in the region due to its great relative abundance and occurrence.

The king angelfish occupies all of these elements in the gulf but appears to have a preference for habitats with sea walls and small individual boulders.

After hatching, the finless fry live off their yolk sack until it is completely absorbed, at which point they begin to eat small zooplankton.