Oödinium is a genus of microscopic parasitic dinoflagellates. They live off salt and fresh water fish, causing a type of fish velvet disease (also called gold dust disease). One species has also been recorded on various cnidarians . Treatment is possible by diluting the commercially available copper salts. Free swimming dinospore is extremely vulnerable to copper. Bringing the water temperature to 30°C helps to release the dinospore from cyst.