Jardini Arowana Care Guide: Managing the "Australian Pearl" Monster Fish

Species Overview#

The Jardini Arowana (Scleropages jardini) is the fish that separates serious monster-fish keepers from everyone else. Native to the rivers of northern Australia and southern New Guinea, this prehistoric-looking predator is sometimes called the "Australian Pearl" for the iridescent crescent markings that ring each scale, glowing gold and rose under tank lighting. It is the only legally exportable Arowana from Oceania, and it commands respect for one simple reason: a fully grown Jardini will outweigh, outlast, and out-bully nearly anything you put in the tank with it.

Unlike its cousin the Asian Arowana, which is regulated under CITES Appendix I and effectively banned in the United States, S. jardini enters the trade legally as captive-bred juveniles. That accessibility is a double-edged sword. Hobbyists buy 4-inch silver babies for $200-$400 and discover three years later that they have a 26-inch fish with the temperament of a freshwater barracuda, a habit of leaping out of the tank, and a footprint requirement most living rooms cannot accommodate.

Adult size

24-30 in (60-76 cm)

Lifespan

15-20 years

Min tank

180 gallons (adult)

Temperament

Highly aggressive

Difficulty

Advanced

Diet

Carnivore (surface predator)

Distinguishing Scleropages jardini from the Silver Arowana#

The most common mistake at the importer level is conflating the Jardini with the South American Silver Arowana (Osteoglossum bicirrhosum). They occupy the same niche — large, surface-hunting predators with elongated bodies and a backward-set dorsal fin — but they are not interchangeable. A Silver Arowana grows longer (up to 36 inches) but stays narrower and more ribbon-like. A Jardini grows shorter but builds bulk; an adult is a thick, muscular slab of a fish.

The easiest visual cue is the scales. Jardinis carry a distinctive crescent of pearlescent pink, gold, or red on each scale, giving the body a stippled, almost mosaic appearance. Silvers are uniformly metallic silver with no scale-edge pigment. Jardini also have a more upturned mouth and a heavier, more arched lower jaw — a fact that becomes painfully relevant when discussing drop eye and bite force later. For a side-by-side comparison of the two species' care requirements, see our Silver Arowana care guide. And if you are weighing all three of the major non-CITES Arowanas, the Black Arowana page covers the third sibling in this prehistoric lineage.

Natural Habitat: The River Systems of Northern Australia and New Guinea#

In the wild, Jardinis inhabit the slow-moving billabongs, oxbow lakes, and floodplain rivers of the Northern Territory, Queensland, and southern New Guinea. These are tannin-stained, warm waters with seasonal flooding cycles that push the fish into shallow, vegetation-choked margins to hunt frogs, large insects, small mammals, and other fish. They are obligate surface predators — their upturned mouth and forward-set eyes are adapted for spotting prey against the sky and lunging upward to take it.

This habitat tells you almost everything you need to know about their captive needs: warm water, soft to moderately hard chemistry, dim overhead lighting, and a long horizontal footprint with open surface area. They evolved to cruise, not to hover. They evolved to leap, not to be confined.

Growth Rate and Maximum Size (24-36 inches)#

Jardinis grow fast in their first two years. A 4-inch juvenile fed appropriately will hit 12-14 inches by its first birthday and 18-20 inches by year two, with growth slowing dramatically thereafter. Final adult size in a properly sized tank is usually 24 to 30 inches; reports of 36-inch fish exist but are rare in home aquaria and almost always come from very large public-display setups.

The growth rate is what catches new keepers off guard. The "cute juvenile" phase lasts about six months. By month nine, the fish that lived happily in your 75-gallon tank is hammering its nose against the front glass on every turn. Plan for the adult, not the juvenile, before you buy.

Water Parameters & Tank Requirements#

Jardinis are not parameter-sensitive in the way a wild-caught Discus or a soft-water tetra is. They tolerate a wide pH range and forgive temperature swings within reason. What they do not forgive is dirty water and undersized enclosures. Their bioload is enormous, and their adult size is non-negotiable.

Minimum Tank Size: Why a 180-Gallon is the Absolute Starting Point#

A juvenile under 8 inches will live happily in a 75-gallon tank for roughly 6 to 9 months. After that, the fish needs to move — permanently — into a tank with a minimum footprint of 6 feet long by 2.5 feet wide, which translates to 180 gallons in a standard six-foot rectangular build, or 225 gallons in a wider variant. An 8-foot by 2.5-foot tank (about 300 gallons) is the realistic long-term home and the size most experienced Jardini keepers eventually settle on.

Length and width matter far more than height. Jardinis are surface fish; they will rarely use the bottom third of the water column. A 6-foot by 2-foot by 30-inch tall tank is worse than a 6-foot by 2.5-foot by 24-inch tank, even though the volumes are similar, because the fish needs front-to-back turning room more than it needs vertical space. A Jardini that cannot turn freely will develop spinal deformities, including a permanent S-curve in the body and a hooked lower jaw.

For an honest look at how rectangular footprints scale with gallonage, our aquarium dimensions guide walks through the actual measurements of standard tank sizes — useful when you are trying to figure out whether a 180-gallon will fit through your basement door. And if you are about to cycle a tank this large for the first time, plan on a fishless cycle of at least 4-6 weeks; the bacterial colony needed to handle a Jardini's eventual bioload takes time to build.

Temperature (75°F-82°F) and pH (6.0-7.5) Stability#

Target a temperature between 75°F and 82°F, with 78°F as a safe middle. Jardinis are warm-water fish and will tolerate the upper end of that range better than the lower. pH should sit between 6.0 and 7.5 — they are not picky about absolute value, but they are picky about stability. A pH that swings two points in either direction during a water change will stress the fish; a pH that drifts slowly toward acidic between water changes is normal and expected for any heavily fed predator tank.

General hardness (GH) of 5-15 dKH is fine. Avoid the extremes: very soft, very acidic water can make them prone to fin and skin infections, and very hard, alkaline water can dull their pearlescent sheen over time. Use a controller-grade heater rated for double the tank's volume, or run two heaters in parallel for redundancy — a heater failure in a 200-gallon tank can drop temperatures slowly enough that you might not notice for 24 hours, by which time the fish is in serious trouble.

Filtration Needs: Over-filtering for High Bio-load Predators#

A Jardini eats like a wolf and produces waste accordingly. The rule of thumb for monster-fish filtration is to turn the tank's total volume over at least 6-8 times per hour through mechanical and biological media. On a 200-gallon tank, that means 1,200-1,600 gallons per hour of true filtration — not the marketing rating on the box, the actual flow with media installed.

The realistic options are a sump (best), two large canister filters running in parallel (good), or a sump combined with a single canister polishing the water (overkill, which is what you want). A wet/dry sump with a generous bio-tower handles the ammonia and nitrite load better than any sealed canister, and it gives you somewhere to hide a heater, a UV sterilizer, and a return pump without cluttering the display tank. Plan on weekly water changes of 30-50% indefinitely; a Jardini tank is not a low-maintenance system.

The "Jump Factor": Securing Weighted Lids and Canopies#

Jardinis jump. This is not a quirk you can train out of them; it is a hard-wired hunting behavior. In the wild, they leap up to 6 feet to take insects, small birds, and lizards from overhanging branches. In your living room, they will leap at lights flicking on, shadows moving past the tank, and the vibration of a closing door. A 25-pound Jardini hitting an unsecured glass lid will launch it across the room.

The lid must be glass or acrylic, must cover 100% of the surface area with no exposed gaps around heaters or filter intakes, and must be weighted down with at least 20-30 pounds of dead weight or actively latched to the rim. A homemade plywood canopy with sliding access doors is the standard solution. Open-top tanks of any kind are not safe with this species, regardless of how high your tank rim sits above the waterline.

Diet & Feeding#

A Jardini's diet shifts dramatically as it grows, and getting the transition right is what separates a healthy 25-inch adult from a deformed, malnourished, or chronically aggressive specimen. The single biggest mistake is feeding live feeder fish for the entire life of the animal — a habit that introduces parasites, locks the fish into one food type, and contributes to drop eye over time.

Juvenile vs. Adult Nutrition: Transitioning from Live to Frozen#

Young Jardinis under 8 inches accept live foods most readily: gut-loaded crickets, mealworms, earthworms, and small feeder shrimp. The goal during this phase is not to feed live forever, but to use the prey response to ease the fish onto frozen and prepared foods. Within the first three to six months in your tank, the fish should be eating thawed shrimp, frozen silversides, and high-quality sinking-or-floating pellets formulated for large carnivores.

By adulthood, a Jardini should accept a varied rotation of frozen krill, silversides, smelt, occasional whole earthworms, and a high-protein floating pellet as the daily staple. Feed adults once or twice a day, offering only what the fish will consume in 60-90 seconds. Over-feeding is the second-fastest way to kill a Jardini (after letting it jump out); the gut is short, and excess food becomes ammonia in the water within hours.

High-Protein Staples: Pellets, Krill, Silversides, and Earthworms#

A balanced adult menu, rotated across the week, looks roughly like this: 50% high-quality floating carnivore pellets (Hikari Massivore, Northfin Cichlid Formula, or equivalent), 25% frozen silversides and smelt, 15% frozen krill and shrimp, and 10% earthworms. Avoid feeder goldfish and rosy reds entirely — they are nutritionally poor (high in thiaminase, which destroys vitamin B1) and they are the most common vector for internal parasites in monster-fish setups.

Live earthworms from a clean, untreated source are the one live food worth using long-term. They are nutritionally dense, parasite-risk is low, and they trigger a strong predatory response without the disease load of feeder fish.

Avoiding "Drop Eye": Floating Food vs. Bottom Scavenging#

Drop eye is the condition every prospective Jardini keeper should know about before buying. Over months and years, the eye of a captive Arowana can rotate downward in the socket, eventually pointing at the substrate instead of forward. The condition is largely preventable but not reversible once established.

The strongest evidence-based theories implicate two factors: persistent downward gazing (caused by the fish constantly searching the substrate for sinking food) and fatty deposits behind the eye (caused by overfeeding rich foods like beef heart or excessive feeder fish). Prevention is mechanical and dietary: feed primarily floating foods to keep the fish looking up, avoid mammalian meats entirely, and consider placing a floating object (a ping-pong ball, a piece of driftwood) on the surface so the fish has something to track upward. Tanks with bright tops and dark, busy bottoms also encourage downward gazing; reverse that contrast where possible.

Tank Mates & Compatibility#

The honest answer to "what can I keep with a Jardini?" is "probably nothing, and definitely not what you want." This is the most aggressive of all commonly available Arowanas, and many experienced keepers run them as solitary display fish for their entire lives. If you must keep tank mates, the rules are strict and the failure rate is high.

The "Solo King" Reputation: Managing Extreme Intraspecific Aggression#

Two Jardinis in one tank, regardless of size, will fight. Even in 500-gallon public-aquarium displays, keepers report that one Jardini will eventually dominate, harass, and often kill the other. The myth that "raising them up together" prevents aggression is widely repeated and almost universally wrong — sibling Jardinis in a juvenile tank get along until they hit roughly 12 inches, at which point they remember they are predators.

Mixing Jardinis with Silver or Black Arowanas is similarly high-risk. The Jardini is faster, more aggressive, and bites harder than its South American cousins. The few successful multi-Arowana setups documented in the hobby involve 8-foot-plus tanks, established hierarchy from a young age, and constant supervision for re-aggression. For most hobbyists, the answer is simple: one Jardini per tank.

Large-Scale Tank Mates: Datnoids, Bichirs, and Large Cichlids#

If you are determined to build a community Jardini tank, you need a 300+ gallon footprint and a roster of fish that occupy the bottom and middle of the water column without challenging the Arowana for surface space. Workable options include:

• Datnoids (Indo and Siamese tigers) — mid-water, similar speed, similar disposition.
• Bichirs — bottom-dwelling, armored, and usually ignored by the Arowana. Good options include the delhezi bichir, endlicheri bichir, and ornate bichir.
• Large cichlids — oscars, green terrors, jack dempseys, and similar New World cichlids that hold their own without being so aggressive they provoke retaliation.
• Large catfish — bottom-dwellers like the tiger shovelnose catfish or larger pleco species that the Arowana cannot easily injure.

Avoid anything that swims at the surface, anything small enough to fit in the Arowana's mouth (which means anything under 6 inches), and anything that flashes bright colors in a way the Arowana might interpret as a competing male.

Why Jardinis Often Fail in Community Monster Tanks#

Most "community Jardini" setups fail in the first year. The pattern is consistent: the Jardini coexists peacefully for several months, then a small environmental change — a water-change shock, a new piece of decor, a tank mate testing the hierarchy — flips a switch and the Arowana begins to attack. By the time the keeper notices, a $300 datnoid or a treasured bichir is dead. Going in with the assumption that any community setup is temporary, and having a backup tank ready to receive displaced fish on short notice, is the only realistic stance.

Common Health Issues#

Jardinis are physically robust fish and rarely succumb to the kind of bacterial infections that plague smaller, more delicate species. The conditions that do affect them are largely mechanical or husbandry-driven, not pathogenic.

Preventing "Drop Eye" and Protruding Lower Jaws#

Drop eye, covered above, is the signature long-term husbandry failure in Arowana keeping. Protruding lower jaw — sometimes called "hooked jaw" or "crooked jaw" — is the related skeletal deformity that develops when a young fish is housed in a tank too narrow to allow full turning. The fish spends years bumping its jaw against the front glass, and the cartilage and bone develop a permanent forward and downward set. Once established, both conditions are essentially irreversible.

Prevention is the only treatment. Buy the right-size tank from the start, feed primarily from the surface, use a dim or shaded lighting setup, and avoid abrupt environmental changes that startle the fish into the front glass.

Ammonia Spikes and Gill Curl in Small Enclosures#

A subadult Jardini in an undersized tank produces enough ammonia in 48 hours to overwhelm a marginal biological filter. Acute ammonia exposure causes a characteristic deformity called gill curl, in which the operculum (gill cover) rolls outward at the edges, exposing the gill filaments. Once the gill cover is permanently deformed, the fish cannot extract oxygen efficiently, and the deformity is cosmetic-and-functional damage for life.

Test ammonia and nitrite weekly, especially during the first six months in a new tank, and run filtration capacity that exceeds the manufacturer's stated rating by at least 50%. If you see ammonia even at 0.25 ppm, do an immediate 50% water change and investigate why your bio-filter is failing.

Treating Bacterial Infections from Physical Injuries (Jumping)#

The most common bacterial infection in a Jardini is a secondary one: the fish startles, slams its face into the glass or the lid, opens a wound on the chin or upper jaw, and the wound becomes infected. Treatment is straightforward — clean water, an aquarium-safe broad-spectrum antibiotic (Kanaplex or Furan-2 dosed in a hospital tank), and elimination of whatever startled the fish in the first place.

Prevention is reducing the startle response: dim the room before turning tank lights on, avoid sudden movements near the front glass, and make sure the lid is secure enough that a leaping fish hits a solid surface rather than dislodging the lid and falling onto a hard floor.

Where to Buy & What to Look For#

Jardinis are not Petco fish. You will source them from specialty importers, dedicated monster-fish stores, and online retailers that ship adult-rated freight. Expect to pay $200-$400 for a healthy 4-6 inch juvenile from a reputable source, and significantly more for sub-adult or specially colored specimens (high-back, royal, or cross-back lines). Avoid wholesale-tank specimens at big-box stores; these fish have usually been through multiple holding tanks, multiple stress events, and arrive with the kind of mechanical damage covered in the inspection checklist below.

Identifying Healthy Juveniles at Your Local Fish Store (LFS)#

The "LFS Inspection Checklist" below is specific to Jardinis and reflects the most common shipping- and handling-related damages this species sustains in the wholesale supply chain. Walk through every point before money changes hands.

Price Points and Shipping Considerations for Large Specimens#

Juvenile pricing breaks down roughly as follows: 4-inch Australian-line juveniles start around $200-$300, New Guinea-line "Gulf Saratoga" variants go for $250-$400, and specially colored "Pearl" or "Royal" lines (selected for redder pearling) climb to $500-$800. Sub-adult specimens (10-14 inches) typically sell for $600-$1,200 from established breeders.

Shipping a Jardini larger than 8 inches gets expensive fast. Boxes need to be insulated, doubled-bagged with pure oxygen, and shipped overnight; a 12-inch fish can run $150-$300 in shipping alone. For fish over 18 inches, freight forwarding and arrival-at-airport pickup is often the only option, and you should plan to drive the fish home in a heated vehicle in a properly insulated transport tub.

Note on legality: the Jardini is one of the few Arowanas that is legal to import and own across most of the United States, but a handful of states (notably California and Hawaii) restrict ownership of large predatory freshwater fish under invasive-species statutes. Check your state and municipal regulations before ordering.

Quick-Reference Cheat Sheet#

A Jardini Arowana is not a pet fish in the casual sense. It is a 20-year living-room fixture, an apex freshwater predator that will dictate the layout of a room and the structure of a weekend. Bought into eyes-open, with the right tank, the right diet, and the right expectations about temperament, it is one of the most rewarding fish in the hobby — a piece of prehistoric biology cruising your living room, watching back. Bought impulsively, it is a heartbreak in slow motion. Decide which one you are buying before the fish goes in the bag.