Like the other members of the family, California killifish are small, no more than about 11 centimetres (4.3 in) in length.

The body is rather thick and oblong in shape, with almost no narrowing of the caudal peduncle, and a squarish tail fin.

Between Goleta Slough and the Tijuana River they occur almost continuously, the frequency of wetlands being sufficient to allow free movement.

They tolerate a wide range of salinities, oxygen levels, and pollution.

The diet consists of a variety of both benthic and planktonic invertebrates, anything from snails to crustaceans to insects, often found by foraging through areas of vegetation flooded by high tides.