What is the biggest fish and the smallest fish?

The biggest fish is the whale shark, which can grow up to 40 feet (12 meters) long and weigh over 20 tons. In contrast, the smallest fish is generally considered to be the Paedocypris progenetica, a species of tiny cyprinid fish found in Southeast Asia, which can measure as little as 7.9 millimeters (0.31 inches) in length. These extremes highlight the incredible diversity within the fish family.