Scatophagus argus

Common Names: Spotted scat, red scat, green scat

Type Locality: India

Range: Widespread in the Indo-Pacific, from Kuwait to Australia and Japan

Taxonomic Troubles: Originally described as Chaetodon argus. FIsh with a large amount of red are sometimes described as S. rubifrons, an invalid name. These fish show considerable variation in coloration, depending on individual, origin, and age.

Size: usually to 38 cm (15inches), larger individuals are encountered; generally sold as small juveniles.

Preferred Water Chemistry: Brackish, marine, occasionally forays into fresh water. Tropical. Temperature 20 to 28 degrees Celsius (68 to 82 degrees Fahrenheit), high pH and hardness.

Difficulty: Very hardy when kept properly, typically sickly and short-lived in fresh water.

Tank Setup: Brackish to marine, must have salt water.

Feeding: Extremely omnivorous. SHould have substantial plant matter in its diet. Will eat just about any fish food--in large quantities.

Breeding: No confirmed reports in captivity. Apparently the young are spawned upriver and migrate into estuaries, then out onto the reef.

Fish Description

Laterally compressed, more rectangular than disc-shaped. Basic coloration greenish yellow, with black spots. Individuals may show more green, yellow, or red coloration. Fin spines reported to be venomous.


This is a spectacular species that is often seen in derelict condition. Although young scats can be found in barely brackish rivers, and the adults will foray into fresh water to feed, the natural habitat of the juveniles is salty estuaries, and adults belong in a full marine environment. Kept in salt water, the scat is an active, friendly, hardy fish, but when sentenced to a freshwater tank, it grows poorly and suffers numerous health problems. Other popular brackish species make good tankmates for juveniles: monos, gobies, mollies, archers. Adult scats are best kept in tanks with full marine salinity.

A large (6-8 foot) tank set up as a mangrove biotope is an ideal way to display a school of scats. The fish will chase each other through underwater branches or roots, always on the lookout for anything edible. They are reported to quickly learn to follow archerfish Toxotes spp. and steal insect they shoot down into the water. Scats become real pets and definitely interact with their keepers.

The genus name, meaning "feces eater," results from early observations of the sewage-feeding proclivities of these fish, but a great many species are equally drawn to the nutrient-rich brew humans divert into the marine environment, or to boats when their sewage pumps are activated. The scat is properly considered an opportunistic omnivore that will exploit any foodsource. Maintaining a brackish aquarium is not simply a case of adding some salt to a tank. Biofiltration especially is a concern, and it is important to keep salinity as constant as possible to avoid killing off the biofilter. Although there is a great appeal in the idea of marine species that can be kept in fresh water, this is not a reality.

"Freshwater" moray eels, gobies, etc., are typically fish adapted to estuaries--or worse, marine fish that can tolerate a freshwater sojourn. That is, they will survive for a while in fresh water, but not for long. The cavalier approach to brackish fishes, simply that they should have some salt added to the water, belies the dedication needed to properly provide for these animals. On the other hand, scats are magnificent specimens when maintained under proper conditions.