This type of pupfish grows to lengths up to 22mm. The top of its head is flat with the mouth situated low under it. Each tooth has a shape resembling the foot of a cat, the point of the tooth being the cat's claw. Males are colored with sides of irridescent metallic blue which changes to metallic green or golden in different light. The fish is whiter toward the anal area, and the opercles are irridescent with a violet sheen on the upper posterior.
Females are generally more yellow than the males.
The Devil's pupfish is primarily an algae eater. Remains of flatworms and beetle larva found with algae may be accidentally ingested while cropping from the rocks. Devil's Hole, Ash Meadows, Nye County, Nevada. Water thermal stability is evident with fluctuations in the amount of dissolved oxygen being due to water circulation from subterranean inlets and outlets, and algae growing on rocks. Encyclopedia of fishes.