The largest recorded hardyhead is 78mm (3in) SL. They are commonly found up to 50mm (2in). They occur in the wild at temperatures from 20°C to 40°C (68 to 104°F) and make very brief excursions into water of 41.8°C (107°F). This is the highest recorded voluntary temperature tolerance of any Australian fish and one of the hottest voluntary temperatures that fish have been recorded at anywhere in the world!
They are generally found in the pools and channels in the spring outflows. The minimum dissolved oxygen tolerated is 0.5 mg O2/L. Their diet consists mostly of green filamentous algae but also includes ciliates, ostracods, insects, hydrobiid snails, detritus, and worms. They are morphologically sexually dimorphic. Virtually nothing is known of reproduction in the wild.