The Three-Lined Grunter, also known as the Scortum barcoo, is a freshwater fish species that belongs to the family Terapontidae. This family of fish is commonly found in tropical and subtropical regions of Australia, Papua New Guinea, and Indonesia. The Three-Lined Grunter is widely distributed in freshwater habitats across eastern and northern Australia, and it is a popular sportfish in many areas.

The Three-Lined Grunter is a medium-sized fish that can grow up to 30 cm in length, but the average size is around 20 cm. Its body is elongated and slender with a slightly compressed and tapering shape. The head is small in proportion to the body, with a large mouth that extends past the eyes. The dorsal fin is long and continuous, with the front portion being spiny, and the rest being soft-rayed. The anal fin is similar in shape and size to the dorsal fin. The body of the Three-Lined Grunter is usually silver or gray in color, with three dark stripes running along the body's length. The stripes may appear black or dark brown and can vary in thickness and intensity.

Three-Lined Grunters are social fish that can be found in groups or schools, and they often form territories around underwater structures such as logs, rocks, and aquatic plants. They are opportunistic feeders and will eat a variety of small aquatic creatures, including insects, crustaceans, and fish. Juvenile Three-Lined Grunters will consume mainly insects and small crustaceans, while adults will feed more heavily on fish.

The Three-Lined Grunter is a popular sportfish in Australia due to its willingness to take a variety of lures and baits, as well as its fighting ability. It is also a popular aquarium fish due to its attractive appearance and peaceful temperament. In the aquarium, it should be provided with plenty of hiding spots such as driftwood, rocks, and plants. A well-filtered aquarium with regular water changes is necessary to maintain good water quality, and they should be fed a varied diet of commercial pellets, frozen and live foods.

In conclusion, the Three-Lined Grunter is a fascinating freshwater fish that is widely distributed in eastern and northern Australia. Its striking appearance and peaceful temperament make it a popular aquarium fish, while its willingness to take a variety of lures and baits makes it a sought-after sportfish. It is an opportunistic feeder that will eat a variety of small aquatic creatures, and it forms territories around underwater structures such as logs, rocks, and aquatic plants.