Arowanas are freshwater bony fish of the family Osteoglossidae, also known as bonytongues. In this family of fish, the head is bony and the elongate body is covered by large, heavy scales, with a mosaic pattern of canals. The dorsal and the anal fins have soft rays and are long based, while the pectoral and ventral fins are small. The name "bonytongues" is derived from a toothed bone on the floor of the mouth, the "tongue", equipped with teeth that bite against teeth on the roof of the mouth. The arowana is a facultative air breather and can obtain oxygen from air by sucking it into the swim bladder, which is lined with capillaries like lung tissue.

 

 Osteoglossids are carnivorous, often being specialized surface feeders. They are excellent jumpers; it has been reported that Osteoglossum species have been seen leaping more than 6 feet (almost 2 metres) from the water surface to pick off insects and birds from overhanging branches in South America, hence the nickname "water monkeys". Arowana species typically grow to around 2 to 3 feet in captivity.Several species of osteoglossid exhibit parental care. They build nests and protect the young after they hatch. All species are mouthbrooders, the parents holding sometimes hundreds of eggs in their mouths. The young may make several tentative trips outside the parent's mouth to investigate the surroundings before leaving permanently.

 

 Arowanas are solitary fish and only appreciate company while young; adults may show dominance and aggression. Some compatible species often partnered with this fish are clown knifefish,pacu, oscars, plecostomus, jaguar cichlids, green terrors, gar, tinfoil barb, siamese tigerfish, and any other semi-aggressive fish that cannot fit in the arowana's mouth.These fishes are best kept with live or frozen feed and they easily outgrow the tank within a span of 8 to 10 months. A large type aquarium of at least 150 gallons is preferable. Australian species are best kept alone in aquaria.