Silver Arowana

Quick summary

The Silver Arowana is an advanced fish suited only to experienced keepers who can provide a 1,000+ litre tank, a secure heavy lid, and long-term commitment, since it grows rapidly to 90cm or more and can live over a decade. If you can’t offer a huge, escape-proof setup with excellent filtration and a varied protein-rich diet, this is not a beginner-friendly choice.

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In this guide:

• Introduction
• Quick Stats
• Appearance
• Natural Habitat
• Tank Size and Setup
• Water Parameters
• Filtration and Equipment
• Diet and Feeding
• Behaviour and Temperament
• Tank Mates
• Breeding
• Common Diseases
• FAQs

Introduction

The Silver Arowana is one of the most iconic freshwater fish in the aquarium hobby, commanding attention with its elongated, serpentine body and remarkable ability to leap from the water’s surface to snatch prey. Native to the vast floodplain ecosystems of the Amazon Basin, this ancient species belongs to the bony-tongue family Osteoglossidae, a lineage that has persisted largely unchanged for millions of years. In many South American cultures, the Silver Arowana is known as the “water monkey” for its acrobatic hunting behaviour, and it occupies a revered place in the ornamental fish trade worldwide.

Keeping a Silver Arowana is not a casual undertaking. These fish grow rapidly and can exceed 90 centimetres in captivity, demanding enormous tanks, powerful filtration, and a carefully managed diet. They are surface-dwelling predators with highly specialised feeding behaviours, and their tendency to jump makes a secure, weighted lid an absolute necessity. For experienced aquarists willing to invest in the space, equipment, and long-term commitment required, however, the Silver Arowana rewards its keeper with a truly spectacular display fish that can live for well over a decade.

This guide covers everything you need to know to provide outstanding care for Osteoglossum bicirrhosum, from appropriate tank dimensions and water chemistry to diet, compatible tank mates, breeding, and disease prevention. Whether you are planning your first Arowana setup or refining an existing one, the information below will help you give this magnificent predator the conditions it deserves.

Appearance

The Silver Arowana possesses one of the most instantly recognisable silhouettes in freshwater fishkeeping. Its body is extremely laterally compressed and elongated, tapering to a broad, fan-shaped caudal fin that merges almost seamlessly with the dorsal and anal fins running along the posterior half of the body. This continuous finnage creates a single, undulating ribbon that propels the fish through the water with surprising grace for its size. The large, upturned mouth is perfectly adapted for surface feeding and houses rows of small, sharp teeth on the jaws, tongue, and palate, the hallmark “bony tongue” from which the family derives its name.

Two short, fleshy barbels protrude from the tip of the lower jaw, serving as sensory organs that help the fish detect vibrations and prey items at the water’s surface. The scales are large, cycloid, and highly reflective, presenting a bright metallic silver colouration in juveniles that gradually develops pearlescent pink, green, or blue iridescence along the scale edges as the fish matures. Under aquarium lighting, these iridescent highlights can be quite striking. The eyes are positioned high on the head and are proportionally large, giving the Arowana excellent binocular vision above the waterline, an essential adaptation for an ambush predator that targets insects, small birds, and bats perching on overhanging branches in the wild.

Juveniles are slender and display a prominent yolk sac for the first few weeks of free-swimming life, along with a darker lateral band that fades as the fish grows. Sexual dimorphism is subtle; males tend to be slightly slimmer and may develop a marginally longer lower jaw, but reliable sexing from external features alone is extremely difficult outside of the breeding season.

Natural Habitat

Osteoglossum bicirrhosum is found throughout the Amazon River basin and its major tributaries, including the Rio Negro, Rio Branco, Rio Madeira, and the Rupununi and Essequibo river systems of Guyana. Its range extends from eastern Peru and Colombia eastward through Brazil and into the coastal drainages of French Guiana and Suriname. This is a truly continental distribution, reflecting the species’ adaptability within the broader category of warm, slow-moving tropical waters.

Silver Arowanas inhabit floodplain lakes, oxbow lagoons, slow-moving backwaters, and the margins of major rivers where the current is gentle. During the annual wet season, the Amazon’s tributaries overflow their banks and inundate vast areas of surrounding forest, creating a seasonally flooded ecosystem known as the várzea or igapó. Arowanas exploit these flooded forests extensively, moving among submerged tree roots and overhanging vegetation to hunt terrestrial and arboreal prey that has been displaced or is accessible from below. The water in these habitats is typically warm, soft, and slightly acidic, often stained dark with tannins from decaying leaf litter. Dissolved oxygen levels can fluctuate, and the Arowana’s ability to gulp atmospheric air using a modified swim bladder helps it survive in oxygen-depleted pools during the dry season.

Understanding this habitat is critical for replicating appropriate conditions in the aquarium. The fish naturally occupies the uppermost water column, patrolling just below the surface. It is accustomed to dim, tannin-stained water, overhead cover from floating plants and branches, and a diet rich in live prey. Recreating these elements, soft, warm water, subdued lighting, surface cover, and ample swimming space, goes a long way toward keeping a healthy and behaviourally enriched Silver Arowana in captivity.

Tank Size and Setup

There is no getting around the fact that Silver Arowanas require exceptionally large aquaria. While juveniles of 10–15 centimetres can be temporarily housed in a 400-litre grow-out tank, they grow rapidly, often adding 5 centimetres or more per month under good conditions, and will need their permanent home within the first year. The absolute minimum tank size for a single adult Silver Arowana is 1,000 litres, but a more realistic and welfare-conscious recommendation is 1,500 litres or above. The critical dimension is length; the tank should be no shorter than 240 centimetres (approximately 8 feet), and a width of at least 75–90 centimetres is necessary for the fish to turn comfortably without bending its body against the glass. Depth is less critical, as Arowanas are surface dwellers, but a minimum of 60 centimetres is advisable.

The single most important piece of equipment after the tank itself is a heavy, tightly fitting lid. Silver Arowanas are legendary jumpers, capable of launching themselves a metre or more above the water’s surface. A loose or lightweight cover will eventually result in a dead fish on the floor. Many keepers use a combination of a solid canopy and weighted glass or acrylic panels, with all gaps sealed or blocked. It is not uncommon for a large Arowana to crack a standard glass lid, so robust construction is essential.

Aquascaping for an Arowana tank should be minimal and practical. A bare bottom or fine sand substrate is preferable, as it simplifies cleaning and prevents food from lodging in crevices. Large pieces of driftwood placed along the back or sides of the tank can provide visual barriers and a more natural aesthetic, but the central swimming space must remain open and unobstructed. Floating plants such as Amazon frogbit or water lettuce can be used to diffuse overhead lighting and give the Arowana a sense of security, provided they do not completely block the surface. Avoid tall, rigid decorations or sharp rocks, as a startled Arowana can injure itself during a sudden dash.

Lighting should be moderate to subdued. Silver Arowanas do not appreciate intense illumination, and overly bright conditions can cause stress, colour fading, and a phenomenon known as “drop eye”, though the exact causes of this condition remain debated. A timer-controlled LED fixture with adjustable intensity, perhaps supplemented with a period of dawn-dusk ramping, is ideal. Keeping the tank in a room with stable ambient lighting and minimal sudden changes in brightness will also help prevent startling.

Water Parameters

Silver Arowanas are relatively tolerant of a range of water chemistries, but they thrive best in conditions that mirror their native Amazonian habitats: warm, soft, and slightly acidic water. Stability is more important than hitting a precise number, so aim to keep parameters consistent rather than chasing a target value through constant adjustment.

Given the enormous bioload a large Arowana produces, maintaining ammonia and nitrite at zero requires robust biological filtration and a disciplined water-change regime. Weekly water changes of 25–30 per cent are recommended as a baseline, and many experienced keepers perform even larger changes of up to 50 per cent. Always match the replacement water’s temperature and chemistry to avoid shocking the fish. If your tap water is significantly harder or more alkaline than the ideal range, consider using a blend of reverse-osmosis water and tap water to achieve the desired softness. The addition of Indian almond leaves or peat filtration media can help naturally lower pH and introduce beneficial tannins.

Filtration and Equipment

Filtration for a Silver Arowana tank must be massively over-specified. A fish that can reach a metre in length and consumes a protein-rich diet produces a corresponding amount of waste, and the filtration system needs to handle this without allowing water quality to deteriorate between maintenance sessions. Most successful Arowana keepers rely on large external canister filters rated for at least double the tank’s volume, or, preferably, a sump-based filtration system. A sump offers several advantages: it increases total water volume, provides ample space for biological media, and keeps heaters, probes, and other equipment out of the display tank where they could be damaged by the fish.

Biological filtration should be the primary focus. High-surface-area media such as sintered glass, ceramic rings, or bio-balls should form the bulk of the filter media. Mechanical filtration using coarse and fine sponges or filter floss will trap particulate waste, and these should be rinsed or replaced regularly to prevent nitrate accumulation. Chemical filtration with activated carbon is optional but can be useful for removing dissolved organics and maintaining water clarity.

Water flow should be moderate. Arowanas are not strong-current fish, and excessive flow at the surface can stress them and interfere with feeding. Position filter outlets to create gentle circulation without generating a strong current in the upper water column. Spray bars oriented along the back glass and angled slightly downward work well for this purpose.

Heating is best provided by two or more high-wattage inline or sump-based heaters, which eliminates the risk of the Arowana damaging or knocking loose a submersible heater in the display tank. Use a reliable digital thermometer or temperature controller with an alarm function to guard against heater failures. An air pump or additional powerhead can serve as a backup for surface agitation, ensuring adequate gas exchange in warmer water where dissolved oxygen levels are naturally lower.

Diet and Feeding

In the wild, Silver Arowanas are opportunistic surface predators with a remarkably varied diet. They feed on insects, spiders, small frogs, lizards, snakes, bats, and even small birds that they snatch from low-hanging branches. They also consume smaller fish and crustaceans found at or near the water’s surface. Replicating this dietary diversity in captivity is essential for long-term health, and relying on any single food item is a recipe for nutritional deficiency.

A well-rounded captive diet should include high-quality, protein-rich pellets formulated for large predatory fish as the staple. These pellets provide balanced nutrition including vitamins and minerals that are difficult to obtain consistently from live or frozen foods alone. Supplement the pellet base with a rotating selection of whole or gut-loaded insects such as crickets, locusts, mealworms, and superworms. Frozen foods including prawns, silversides, smelt, and lance fish are excellent additions and are readily accepted by most individuals. Earthworms are a superb food source, nutritionally rich, eagerly consumed, and easily obtained.

Live feeder fish are a traditional Arowana food but should be used sparingly and sourced with extreme caution. Commercially bred feeder fish such as goldfish and rosy reds are frequently kept in poor conditions and can carry parasites and bacterial infections. If you choose to offer live fish, quarantine them for at least two weeks and gut-load them with nutritious food beforehand. Many experienced keepers avoid live feeder fish entirely, finding that a combination of pellets, insects, and frozen foods provides superior nutrition without the disease risk.

Feed juvenile Arowanas two to three times daily, offering only what they can consume in a few minutes. As the fish matures, reduce feeding frequency to once daily or even every other day for large adults. Overfeeding is a common mistake and leads to fatty liver disease, obesity, and accelerated water quality degradation. Fasting one day per week is a sensible practice for adult fish. Avoid feeding mammalian meats such as beef heart or chicken, as these contain fats that fish cannot metabolise efficiently and can contribute to organ damage over time.

Behaviour and Temperament

Silver Arowanas are generally solitary, territorial fish that do best when kept individually. In the wild, adults occupy and patrol a defined territory along the water’s surface, and this behaviour translates directly to captive life. A single Arowana will claim the entire surface of its aquarium and may become aggressive toward any fish that encroaches on this zone. This territorial behaviour intensifies as the fish matures and grows into its full size.

Despite their predatory nature, Silver Arowanas can become remarkably tame with consistent, patient interaction. Many individuals learn to recognise their keeper and will approach the front glass in anticipation of feeding. Some can even be trained to accept food from the hand, though caution is advisable, their small teeth can deliver a sharp nip. This intelligence and responsiveness are part of what makes Arowanas so appealing to dedicated hobbyists.

Arowanas are most active during dawn and dusk, reflecting their crepuscular feeding habits in the wild. During the day, they often cruise slowly just below the surface, occasionally pausing to hang motionless in one spot. Sudden movements, loud noises, or changes in lighting can startle them, and a panicked Arowana in a confined space can injure itself severely by crashing into tank walls or the lid. Placing the tank in a low-traffic area of the home and avoiding abrupt environmental changes will help keep stress levels manageable.

The phenomenon of “drop eye,” in which one or both eyes develop a permanent downward gaze, is frequently observed in captive Silver Arowanas. While the exact cause remains debated, contributing factors are thought to include fatty deposits behind the eye from an overly rich diet, reflections from the tank bottom or sides, and the fish constantly looking downward at food or activity below the waterline. Feeding at the surface, using a dark or non-reflective substrate, and providing floating cover may help reduce the risk.

Tank Mates

Choosing tank mates for a Silver Arowana requires careful thought. Any fish small enough to fit in the Arowana’s mouth will eventually become a meal, and that mouth is considerably larger than it first appears. Ideal companions are large, robust species that occupy the middle or lower water column and are neither aggressive enough to harass the Arowana nor so passive that they become targets. The tank must be large enough to accommodate all inhabitants comfortably, with distinct zones for each species. In many cases, a species-only setup is the safest and simplest option, but a well-planned community of large fish can work beautifully.

Good tank mates

• Oscar (Astronotus ocellatus), a robust, similarly sized cichlid that generally holds its own and occupies the mid-water zone.
• Common Pleco (Hypostomus plecostomus), a large, armoured bottom-dweller that is typically ignored by Arowanas and helps with algae control.
• Sailfin Pleco (Pterygoplichthys gibbiceps), another well-armoured catfish that grows large enough to avoid predation and stays near the substrate.
• Clown Loach (Chromobotia macracanthus), a sociable bottom-dwelling species that, when kept in groups, grows large enough to coexist safely with an adult Arowana.
• Giant Gourami (Osphronemus goramy), a peaceful, very large labyrinth fish that coexists well provided the tank is suitably spacious.
• Bichir (Polypterus spp.), Heavily armoured, bottom-dwelling predators that stay out of the Arowana’s surface territory.
• Fire Eel (Mastacembelus erythrotaenia), a large, nocturnal spiny eel that occupies a completely different niche and is rarely bothered by Arowanas.
• Peacock Bass (Cichla spp.), a large, predatory cichlid that is robust enough to share space, though both fish need ample room.

Fish to avoid

• Neon Tetra (Paracheirodon innesi), far too small; will be consumed almost immediately.
• Guppy (Poecilia reticulata), Tiny livebearers that are nothing more than a snack for an Arowana.
• Flowerhorn Cichlid, highly aggressive and territorial, likely to harass or injure the Arowana in a confined space.
• Red Devil Cichlid (Amphilophus labiatus), an extremely belligerent cichlid known for attacking tank mates of any size.
• African Rift Lake Cichlids, Require hard, alkaline water that is incompatible with the Arowana’s preferred soft, acidic conditions.
• Corydoras Catfish, too small and vulnerable; their defensive spines can also lodge in the Arowana’s throat if swallowed.
• Freshwater Angelfish (Pterophyllum scalare), Slow-moving and slender enough to be easily consumed by a mature Arowana.
• Tiger Barb (Puntigrus tetrazona), Small, nippy fish that may harass the Arowana’s finnage before eventually being eaten.

Breeding

Breeding Silver Arowanas in captivity is extraordinarily difficult and is almost never achieved in home aquaria. The primary obstacle is space; in the wild, breeding occurs in large floodplain lakes during the rainy season, and the courtship and spawning behaviours require vast territories that simply cannot be replicated in a typical aquarium. Virtually all Silver Arowanas in the trade are either wild-caught or pond-bred in tropical fish farms in South America and Southeast Asia, where they are given access to large earthen ponds that better approximate natural conditions.

Silver Arowanas are paternal mouthbrooders. After a prolonged courtship that involves the pair swimming in close parallel circles near the surface, the female deposits a relatively small number of very large eggs, typically 100 to 250, each measuring roughly 12–16 millimetres in diameter. The male then fertilises the eggs and immediately takes them into his mouth, where they will be incubated for approximately 50 to 60 days. During this period, the male does not eat. The fry hatch within the buccal cavity and remain there, nourished by their substantial yolk sacs, until they have absorbed enough yolk to begin free-swimming and independent feeding. Released fry are already 7–10 centimetres long and closely resemble miniature adults, though they retain the yolk sac for several days after release.

For the rare keeper with access to a pond or an exceptionally large indoor facility, typically well above 10,000 litres, successful breeding requires a compatible, sexually mature pair (usually at least three to four years old), excellent water quality, and a simulation of seasonal environmental triggers such as temperature drops, fluctuating water levels, and increased feeding in the period leading up to spawning. Even under ideal conditions, breeding attempts frequently fail, and aggression between incompatible pairs can be severe. Given these challenges, breeding Silver Arowanas is best left to specialist farms and public aquaria with the resources to accommodate their needs.

Common Diseases

Silver Arowanas are hardy fish when kept in appropriate conditions, but their size and predatory diet make them susceptible to a handful of common health issues. Prevention through excellent water quality, a varied diet, and stress reduction is always preferable to treatment, as medicating a tank of 1,000 litres or more is both expensive and logistically challenging.

Anchor worm (Lernaea) and fish lice (Argulus) are ectoparasites frequently encountered in wild-caught or pond-raised Arowanas. These parasites are visible to the naked eye and attach to the skin, fins, or gill covers. Treatment involves careful manual removal of individual parasites with forceps, followed by a course of anti-parasitic medication such as a product containing diflubenzuron or organophosphate-based treatments formulated for ornamental fish. Quarantining all new arrivals for at least four weeks before introduction to the display tank is the best way to prevent these parasites from establishing themselves.

Ichthyophthirius multifiliis, commonly known as white spot or ich, can affect Arowanas, particularly juveniles or individuals stressed by poor water quality or temperature fluctuations. The characteristic white cysts on the skin and fins are easily identified. Raising the water temperature gradually to 30–32 °C and treating with a half-dose of a malachite green and formalin based medication is the standard approach, as Arowanas can be sensitive to full-strength treatments.

Drop eye is a condition rather than a disease, characterised by one or both eyes developing a permanent downward orientation. As discussed earlier, it is thought to be linked to fat deposits, genetics, and environmental factors. While rarely life-threatening, it is cosmetically undesirable and largely irreversible once established. Surgical intervention has been attempted by some keepers and veterinary surgeons, but results are inconsistent and the procedure carries significant risk.

Gill curl is another condition seen in captive Arowanas, in which the gill covers begin to curl outward, exposing the delicate gill filaments. This is typically attributed to poor water quality, particularly chronically elevated nitrate levels, and insufficient water changes. Early-stage gill curl can sometimes be corrected by improving water quality dramatically and, in some cases, by carefully trimming the curled portion of the operculum under sedation, a procedure best performed by an experienced aquatic veterinarian.

Bacterial infections, including fin rot and ulcerative lesions, can develop secondary to stress, injury, or poor water conditions. Arowanas that have jumped and been returned to the tank, or that have collided with hard surfaces during a fright response, are particularly vulnerable. Treatment typically involves improving water quality, adding aquarium salt at a low concentration (1–3 grams per litre), and administering an appropriate antibiotic or antibacterial medication if the infection is severe.

FAQs

How fast do Silver Arowanas grow?

Silver Arowanas are among the fastest-growing aquarium fish. Under optimal conditions with frequent feeding and excellent water quality, juveniles can grow 5–7 centimetres per month during their first year. Growth slows somewhat after the first 12–18 months, but a fish can easily reach 45–60 centimetres within its first year of life. This rapid growth rate is why it is essential to plan for a permanent, large tank from the outset rather than attempting to “upgrade as the fish grows,” which often leads to stunting and health complications.

Can I keep more than one Silver Arowana in the same tank?

Keeping multiple Silver Arowanas together is extremely risky and generally inadvisable unless you have an exceptionally large system, typically well in excess of 5,000 litres. In smaller enclosures, conspecific aggression is virtually guaranteed, and dominant individuals will relentlessly harass subordinates, leading to stress, injury, and death. Some large public aquaria and specialist keepers maintain groups of six or more to distribute aggression, but this requires a scale of tank that is beyond most private hobbyists. For the vast majority of keepers, a single specimen is the safest approach.

What should I do if my Arowana jumps out of the tank?

If you find your Arowana on the floor, act quickly. Gently return the fish to the water, supporting its body fully to avoid further injury to its spine or internal organs. Dim the lights to reduce stress and add a mild dose of aquarium salt (1–2 grams per litre) along with a stress coat product to help repair damaged mucus membranes. Monitor the fish closely for secondary infections over the following days. Even fish that appear unresponsive can sometimes recover if returned promptly. Moving forward, reinforce the lid to ensure the incident cannot recur.

Do Silver Arowanas need live food?

No, Silver Arowanas do not require live food and can be raised on a complete diet of high-quality pellets, frozen foods, and commercially bred insects. Live food carries a significant risk of introducing parasites and diseases, and its nutritional profile is often inferior to prepared alternatives. While some keepers offer live food as enrichment, it should never form the dietary staple. Most captive-bred or long-term captive Arowanas readily accept pellets and frozen items once trained.

Why does my Arowana have drop eye?

Drop eye is a multifactorial condition that remains incompletely understood. Suspected causes include the accumulation of fatty deposits behind the eye from an excessively rich diet, the fish habitually looking downward at reflections, substrate, or activity below the tank, and possible genetic predisposition. To minimise the risk, feed a balanced and not overly fatty diet, use a dark or non-reflective substrate, provide floating cover or plants at the surface, and position the tank so the Arowana is not constantly looking downward at foot traffic or other stimuli below its eye line.

Related Guides

• Asian Arowana (Scleropages formosus), a closely related and highly prized species with similar care requirements but distinct legal and conservation considerations.
• Black Arowana (Osteoglossum ferreirai), the Silver Arowana’s congener, with a striking dark juvenile colouration and largely overlapping husbandry needs.
• Oscar (Astronotus ocellatus), a popular large cichlid frequently kept alongside Arowanas, with its own comprehensive care requirements.
• Giant Gourami (Osphronemus goramy), another massive freshwater species often housed with Arowanas in community predator setups.
• Bichir (Polypterus spp.), Prehistoric bottom-dwellers that make excellent Arowana companions and share a similar appeal for keepers of ancient fish lineages.