The short answer
An arowana needs a tank at least 3× its adult body length and 1.2× its body length in width so it can turn without scraping. It needs a heavy, fully secured lid — jumping is the single most common cause of death in captive arowana. Water: pH 6.0–7.5, 26–30 °C, ammonia and nitrite at zero.
Minimum adult tank size by species
| Species | Adult length | Minimum adult tank | Notes |
|---|---|---|---|
| Silver arowana (Osteoglossum bicirrhosum) | 90–120 cm | 1,000 L+, footprint from about 250 × 100 cm | The largest and the most commonly under-housed. Most silvers sold are outgrown within 3 years. |
| Asian arowana (Scleropages formosus) | 60–90 cm | 600–1,000 L, footprint from about 180 × 75 cm | CITES Appendix I. Legal trade requires documentation — verify the paperwork and the current UAE requirements before you buy. |
| Jardini arowana (Scleropages jardinii) | 50–65 cm | 500–700 L | The most aggressive of the three. Usually kept alone. |
A 60 cm juvenile tank is a two-year rental, not a home. Plan the final aquarium — including how it gets through the door — before the fish is ordered.
The lid is the most important piece of equipment
Arowana are surface hunters that evolved to leap at insects in overhanging branches. In an aquarium they will hit the cover hard, and an unsecured lid does not stop them.
- Use a rigid, weighted, full-coverage lid. Not a mesh screen. Not a glass sheet resting on plastic clips.
- No gaps. Filter outlets, feeding hatches and cable cut-outs are all escape routes. A gap wide enough for the fish's head is wide enough for the fish.
- Leave headroom. A fish that jumps into a lid 5 cm above the water hits it harder than one with 20 cm to slow down.
- Startle is the trigger. Sudden lights-on in a dark room, a shadow over the tank, an unexpected bang. Use a dim night light or ramp your lighting.
This is not a theoretical risk. It is the leading way expensive arowana die.
Water parameters
| Parameter | Target |
|---|---|
| Temperature | 26–30 °C (stable matters more than the exact figure) |
| pH | 6.0–7.5 |
| Ammonia / nitrite | 0 ppm, always |
| Nitrate | Under 40 ppm; under 20 ppm is better for long-term fin and eye condition |
| Hardness | Soft to medium. They tolerate a range — they do not tolerate swings. |
| Water change | 25–30% weekly minimum. These are large, messy carnivores. |
Filtration should be sized for a heavy carnivore load — in practice 8–10× turnover per hour, usually via a sump or multiple canisters. Strong flow is fine; a fish forced to swim against a jet all day is not.
Feeding: the part that quietly causes problems
Arowana are carnivores, and feeding them is theatrical, which is exactly why people get it wrong. Overfeeding pollutes the water, encourages fussiness, and is widely associated with drop eye.
| Good staples | Occasional | Avoid |
|---|---|---|
| High-quality carnivore pellets, earthworms, prawns/shrimp (shell on) | Crickets, superworms, mussel, whole fish of known origin | Feeder goldfish and rosy reds — disease vector and high in thiaminase. Mammal meat (beef heart, chicken) — fat the fish cannot process. |
- Juveniles: 2–3 small feeds per day.
- Adults: once a day, or 4–5 times a week. A slightly hungry arowana is a healthy one.
- Feed to the fish, not to the audience. Stop when interest drops, not when the food runs out.
- Train onto pellets early. A fish that only eats live food is a fish you cannot easily feed when you travel.
Drop eye
Drop eye is the permanent downward rotation of one or both eyes. It is not fully explained, but the most commonly cited contributing factors are a high-fat diet, and a fish that spends years looking downward — at food falling to the bottom, at a bright reflective floor, or at activity below a tall tank. It is cosmetic rather than fatal, but it does not reverse. Feeding at the surface, keeping fat content moderate, and avoiding tall narrow tanks are the sensible precautions.
Tank mates
The rule is simple: anything that fits in the mouth is food, and anything that competes for the surface is a fight. Good tank mates occupy the bottom and mid-water and are too big to swallow.
| Usually works | Usually fails |
|---|---|
| Large plecos, bichirs, datnoids, silver dollars, large catfish, stingrays (in very large systems), tinfoil barbs | Anything under about 15 cm. Other surface fish. Fin-nippers. Two arowana in anything but a very large tank. |
A single arowana in a species-only tank is a completely legitimate setup, and it is the lowest-risk one. Jardini in particular are often best kept alone.
Buying: what to actually look at
Colour photographs sell arowana. Behaviour tells you whether the fish is healthy.
- Swimming: steady, level cruising. Not pacing the glass, not hanging in a corner.
- Body line: straight spine, no kinks, no pinched belly.
- Fins: fully extended, no clamping, no split or blown-out edges.
- Gills: flat gill plates, no curling. Gill curl is a permanent deformity linked to poor water quality and low oxygen while growing.
- Barbels: both present, straight, not broken or receding.
- Feeding: ask to see it eat. A fish that will not eat in the shop will not eat in your car.
Quarantine anyway
An expensive fish is not a clean fish. Quarantine gives you a baseline for breathing, appetite, waste and behaviour — so that when something changes, you can see it. Two to four weeks in a bare, well-filtered, well-covered tank.
Frequently asked questions
What size tank does an arowana need?
At least 3× its adult body length in tank length, and 1.2× in width. Practically: 1,000 L+ for a silver arowana, 600–1,000 L for an Asian arowana, 500–700 L for a jardini.
How long do arowana live?
Commonly 10–20 years in captivity, and longer in well-maintained systems. This is a decade-plus commitment to a very large tank.
Why do arowana jump?
They are surface predators that evolved to leap for insects. Startle triggers it — sudden light, a shadow, a noise. A rigid, weighted, gap-free lid is mandatory, not optional.
Can I keep two arowana together?
Only in a very large system, and even then it is risky. Arowana are territorial. Keepers who do it successfully typically use tanks of several thousand litres and either a group of six-plus (to spread aggression) or heavy visual breaks — not a pair.
What causes drop eye in arowana?
It is not fully settled. The most commonly cited contributors are a high-fat diet and years of looking downward. It is cosmetic, permanent, and easier to avoid than to fix.
Can I feed my arowana feeder goldfish?
Don't. Feeder fish are a reliable route for parasites and disease, and goldfish are high in thiaminase, which destroys vitamin B1 over time. Use quality pellets, earthworms and prawns instead.
Related reading: how to cycle a new aquarium — never put an arowana into an uncycled tank. Aquarium filtration basics for sizing the filter to a heavy carnivore load, and aquarium maintenance in Dubai for keeping a large tank stable through summer.