Tetraodon nigroviridis

Tetraodon nigroviridis is one of the pufferfish known as the green spotted puffer (the other being Tetraodon fluviatilis). It is found across South and Southeast Asia in coastal freshwater and brackish water habitats. Tetraodon nigroviridis reaches a maximum length of about 15 cm (5.9 in).

Ecology
Adult Tetraodon nigroviridis are found in freshwater streams, rivers, and floodplains. It is also found in mangrove forests. Diet consists of small invertebrates including molluscs and crustaceans and some plant material. It can also survive on a combination of aquarium food; such a combination would be small snails, and shrimp or krill. This species may also be lepidophagous.

Genetics
Tetraodon nigroviridis has the smallest known vertebrate genome and has thus been selected as a model organism for genetics. In 2004 a draft of its genome sequence was published.

Commercial importance
Tetraodon nigroviridis is not a food fish, but has some value as bait and is very widely traded as an aquarium fish, and is sometimes mistaken as the Ceylon Puffer, or Tetraodon fluviatilis. Tetraodon nigroviridis also has some degree of value as a lab animal, in particular in the field of genetics, because it has the same number of genes as human beings but in a genome about one-tenth the size.

Aquarium care
While Tetraodon nigroviridis may be found in fresh as well as brackish water in the wild, under aquarium conditions this species appears to do best in brackish conditions where the salinity is maintained at around 50% that of normal seawater. Adults of this species may also be kept in saltwater aquaria. Since these fish produce a large amount of waste they are best given 29 gallons of water or more per specimen.