Its common name derives from the dominant males' body pattern, which bears some resemblance to the Flag of the United States.

Flagfish are small, robust fish, 6 centimetres (2.4 in) in length, with a truncated snout which has been compared to that of a bulldog.

[2] The flagfish normally occurs in shallow, well vegetated freshwater habitats such as backwaters, marshes, canals and ditches but it has occasionally been recorded in slightly brackish water.

[4] They are often used to naturally control hair algae in suitable aquariums, as they are one of the only fish to consume it in an impactful volume.

[5] The flagfish was described by George Brown Goode and Tarleton Hoffman Bean in 1879 with the type locality given as Lake Monroe, Florida.