Phaeoptyx conklini is a secretive, hidden-living species found deep in caves or under sheltered ledges.
The cardinalfish is largely unobserved during daylight hours and emerges at night to form large feeding aggregations one to five meters above caves to feed on small crustaceans.
The fish are often found on shallow rock and coral bottoms, in empty shells, over boulders, or empty containers.
In the Gulf of Honduras, this species was collected in shallow forereef, patch reef, rocky, mangrove, shallow sandy bottom, and seagrass habitats, but was not common in slope habitats
It is common where Acropora palmata occurs
Distinct mating occurs during courtship and spawning, and spawning may occur throughout the year.
Phaeoptyx conklini a mouthbrooder with a cheek pocket for incubating eggs.
The cardinalfish is a nocturnal predator that feeds on small crustaceans.
Amia conklini Silvester, 1915
Apogon conklini (Silvester, 1915)