It seems that every major group of aquarium fish has its hardcore enthusiasts. However, few are as valued–even revered–as much as the arowana. That is not so surprising, given the mystique that surrounds this animal. It is not just a beautiful and interesting aquarium fish, but is to countless keepers downright exciting to have and care for. However, while most hobbyists would agree that the arowana is amazing to observe in captivity, it is certainly not for everyone. Many considerations should be made prior to obtaining one of these so-called monster fishes.
If the arowana appears to be ancient to some, it is for good reason. Archaic species belonging to the arowana superorder Osteoglossomorpha perhaps date all the way back to the late Jurassic period, considerably older than most extant bony fish forms. Their fossils have been discovered on every continent except Antarctica. Modern examples, sometimes referred to as the bonytongues, belong to the family Osteoglossidae. The osteoglossids are exclusively freshwater dwelling fishes that are characterized by a tongue-like bone on the bottom of the mouth; this structure has teeth that communicate with teeth on the upper part of the mouth.
Like their cousins the arapaimas, arowanas are capable of breathing air. However, unlike the arapaima which is an obligate (i.e. dependent) air-breather, arowanas are facultative air breathers (i.e. can exploit, but do not depend upon, air to breath). This is accomplished by way of a lung-like swim bladder. When air is drawn into the bladder, gas exchange takes place at the interface of numerous, fine capillaries.
Members of the family are highly recognizable, having a long, slender, slightly laterally compressed body that tapers somewhat toward the tail. The head is rather large and upturned. The mouth is large. It bears the big, heavy scales that are common in many groups of related primitive fishes. They are rather large for a freshwater fish, reaching lengths of a few feet in captivity, though wild specimens roughly twice that size can be found. These surface-dwelling predators are capable of jumping several feet out of the water in pursuit of terrestrial prey such as flying insects and even birds. A varied diet of meaty foods such as silversides, crickets and krill are acceptable foods in the aquarium.
Morphological traits are fairly well conserved in the group, considering its long evolutionary history. Even though they predate the divergence of the continents, their extant forms are similar worldwide. Asian forms are most easily distinguished from the popular Australian forms by their longer pectoral and pelvic fins and a longer, pointier face. Asian arowanas (regarded by natives as auspicious due to the animal’s overall dragon-like appearance) usually are silvery, golden or greenish in color, though very impressive “super” red forms are also available. The gold arowana (Scleropages jardinii) is one example of an Australian species kept by aquarists. All present-day New World arowanas occur in South America; of these, the black (Osteoglossum ferreirai) and silver (O. bicirrhosum) arowanas are best known. The African arowana (Heterotis niloticus), yet another highly desired species, is known as one of the most demanding and delicate in captivity. Aquarium care (and especially price) will vary from species to species.
Due to overfishing (at least in part because of their popularity as aquarium pets and “good luck” charms), arowanas are highly protected in many parts of the world. Before selecting an arowana to purchase as an ornamental fish, it is best to review the current conservation status of the species. In many cases, it will be possible to obtain farm-raised specimens. These are not only better choices for environmental reasons, but will also adapt more easily to life in the aquarium.
Given the morphology and behavior of the arowana, certain requirements for their housing should be self-evident. Most obvious is their need for extensive space. Therefore, a large (usually more than a couple hundred gallons capacity) aquarium is necessary. Longer and deeper, rather than taller, tank shapes are preferable. The aquascape should be open, especially at the surface, with little physical obstruction from stones, wood, etc. As these powerful animals have been known to break glass tank panels, acrylic construction is always best. And, of course, keeping these jumpers confined to the tank will be pretty much impossible without a heavy, secure, full cover.
While arowanas are generally tolerant of a wide range of water chemistry, it is best to research the optimal parameters for the desired species and maintain them as closely as possible.
Arowanas are not especially social. In fact, many (especially Asian varieties) can be vicious and therefore should be housed alone. Any tankmates should not only be large and sturdy enough to resist the arowana’s aggressive and predatory impulses, but should also tend to occupy middle or bottom parts of the tank. For this reason, fishes such as freshwater eels, knifefishes and catfishes may be acceptable cohabitants. Fin-nipping fishes of any species (including many cichlids) should be excluded.
Provided with appropriate housing and compatible tankmates, an arowana can easily be kept in captivity for as long as a decade. While such an effort may seem costly and time-consuming to some, there are clearly many arowana enthusiasts out there who find this captivating creature well worth it.