Silver Arowana — Jumping Out of Tank
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⚠️ Urgent · behavioral

Why Is My Silver Arowana Jumping? Instinct, Triggers and How to Keep It in the Tank

Osteoglossum bicirrhosum
🐟 Species: Silver Arowana
🔬 Problem: Jumping Out of Tank
📋 Category: behavioral
⚡ Urgency: urgent

Updated September 28, 2026 · FishCare AI Editorial Team

Short answer: Jumping is normal for a silver arowana: in the Amazon it leaps out of the water to snatch insects, spiders and even small birds from overhanging branches. It will jump in any tank, so the fix is a heavy, fully sealed lid today, not medication. If it is jumping far more than usual, check the water and look for what is startling it.

Most fish that jump are trying to escape something. The silver arowana is different: jumping is how it feeds. It hunts along shorelines and through flooded forest, and supplements its limited diet of aquatic prey by leaping out of the water to take terrestrial and tree-dwelling animals.[1] Stomach-content studies show that insects and other arthropods make up the bulk of what it eats,[2] and wild arowana have even been caught with rodents filling their stomachs.[3] A fish built to launch itself at anything that moves above the surface does not lose that instinct in an aquarium.

That changes how to think about the problem. Asking whether jumping is "normal" gets a yes; the useful questions are whether the tank can contain the jumps, whether something is triggering far more of them than usual, and whether the fish has already hurt itself. An arowana that lands on the floor can die quickly, and one that repeatedly hits a lid can injure its jaw, eyes and scales. Deal with the lid first, then work through the triggers below.

Why Do Silver Arowana Jump? The Common Causes

Hunting Instinct: Built to Leap for Prey

Most Likely

Silver arowana are surface feeders. The mouth points sharply upward, which lets the fish take prey from below while swimming just under the surface, and it also jumps out of the water to feed on large insects such as beetles.[4] Accounts of the species in the wild describe fish waiting near the shore and leaping to take large insects, other fish and small birds from low branches.[5] A study that filmed arowana feeding found that they open their mouths unusually wide during a leap, which may help them hit prey whose position is distorted by the water surface.[1]

In an aquarium the same behaviour fires at a hand over the tank, a moth at the light, a feeder fish at the surface or simply the approach of feeding time. Aquarists who keep them describe arowana leaping at the slightest hint of food.[6] This is the reason every experienced keeper treats a secure lid as essential rather than optional. A healthy, well-kept arowana will still jump; the aim is to make sure it never lands anywhere but back in the water.

Fright: Sudden Light, Movement or Noise

Most Likely

The second trigger is fear. Arowana are known to leap out of aquariums at a hint of fear as well as food, and these jumps are the ones that cause serious injuries and deaths.[6] Common triggers are the room light or tank light switching on in a dark room, someone walking quickly past the tank, a door slamming, a hand reaching in, and netting or chasing the fish during maintenance. Light and sound are both recognised physical stressors for fish.[8]

Fright jumps tend to happen at predictable moments — lights on in the morning, cleaning day, a busy room in the evening — and are more violent than feeding leaps. A fish that is kept in too small a tank has less room to turn away from a threat and is more likely to go straight up.

A Tank Too Small for an Adult Arowana

Possible

Silver arowana are sold at a few centimetres long but grow to about 90 cm in total length and up to around 6 kg.[4] A long-bodied fish that size cannot turn comfortably in an ordinary aquarium, and keepers report that arowana in cramped tanks become restless, nervous and picky, and that the same fish calm down noticeably in far larger tanks or ponds.[6] Crowding and a lack of swimming space are recognised stressors that affect behaviour and immunity.[8]

If your arowana jumps more as it grows, the tank has probably become too small. The long-term fix is space — a tank several times the fish's length and at least as wide as it is long — not simply a stronger lid, although you need both.

Poor Water Quality or Low Oxygen

Possible

Fish that are short of oxygen gather at the surface and try to gulp air,[7] and a large predator eating meaty food produces a lot of waste. Ammonia and nitrite both stress fish, and fish affected by nitrite toxicity seek out oxygen-rich areas and pipe at the surface.[7] An arowana that spends more time right at the top, breathes fast and jumps more than usual may be responding to the water, not to prey.

Warm water holds less oxygen than cool water,[7] so the risk is highest in a heavily stocked tank at the top of the arowana's range. In a healthy tank ammonia should always read zero; any measurable ammonia means the filter cannot keep up.[10] Test before you assume the jumping is behavioural.

Tankmates, Parasites or Skin Irritation

Less Common

Less often, the arowana is being harassed. Aggression and territorial pressure from other fish are listed stressors,[8] and an arowana pestered by a fin-nipper or a fast cichlid may bolt upward. Watch the tank for a few minutes at different times of day before ruling this out.

Skin and gill parasites cause fish to flash — dart and rub against objects — and some affected fish lose their appetite and become lethargic.[9] A jumping arowana that is also scratching on decor, breathing fast or showing cloudy patches on the skin should be checked for parasites rather than treated as a behaviour problem.

How to Work Out Why Your Arowana Is Jumping

Start with the lid, then use a few days of observation and a water test to find out whether the jumps are normal hunting, fright or something wrong with the tank.

  1. Check the lid for any gap the fish could get through

    Look at every opening: filter and heater cut-outs, feeding hatches, the gap at the back for cables, and the joins between glass panels. An arowana will find the smallest gap during a hard jump. Check that the lid is heavy or clipped down, because an adult can lift a loose cover. Aquarists who keep arowana recommend weighting the cover down.[6]

  2. Record when the jumps happen

    For two or three days, note the time and what was happening just before each jump. Jumps around feeding or when a hand or insect is above the water are hunting; jumps when a light comes on, someone walks past or the tank is being cleaned are fright.[6] This tells you which triggers to remove.

  3. Test the water and watch the breathing

    Test ammonia, nitrite, nitrate, pH and temperature. Ammonia should read zero,[10] and the arowana's range is roughly 24 to 30 °C.[4] Watch the gill covers: fast breathing with the fish hanging at the surface suggests low oxygen or poor water rather than normal hunting.[7] Test immediately whenever behaviour changes.[10]

    Recommended: Water test kit and thermometer
  4. Measure the fish against the tank

    Compare the arowana's length with the width of the tank. If it cannot turn around without bending sharply, the tank is too small and restlessness and jumping will continue however well you secure it.[6][8]

  5. Inspect the fish for injuries after a jump

    Look closely at the lower jaw and barbels, the eyes, and the scales along the back and sides. Split lips, missing or lifted scales, cloudy eyes and red marks are signs the fish has been hitting the lid or has been out of the tank. Any break in the skin or lost scale is an opening for infection,[8] and skin damage makes it harder for a fish to keep its fluid balance.[9]

How to Stop a Silver Arowana Jumping Out

  1. Fit a heavy, fully sealed lid today

    Cover the whole tank with a solid glass or acrylic lid, or a rigid screen under a hood, and block every cut-out with foam or mesh. Weight or clip it down.[6] If you cannot seal it immediately, lower the water level several centimetres as a temporary measure so the fish has less momentum at the surface and further to go to reach the rim.

  2. If the fish has jumped out: return it and watch for infection

    Pick it up gently with wet hands or a wet towel, supporting the whole body, and return it to the tank at once. Keep the lights off for a few hours so it can settle. Handling strips protective mucus from the skin,[8] so check the water is spotless and watch daily for cloudy skin, red patches or fungus-like growth at any wound over the following week. Internal injuries may not show at first; a fish that lies on the bottom, stops eating or swims abnormally after a fall needs a vet.

  3. Remove fright triggers

    Turn on the room light before the tank light, or use a light with a gradual dimming start. Place the tank away from doors and walkways, or cover the back and sides so movement around the room is less visible. Avoid chasing the fish with a net during maintenance, since handling is itself a major stressor.[8]

  4. Correct water quality and oxygen

    Increase surface agitation or aeration, do partial water changes until ammonia and nitrite read zero, and review filtration for a large, heavily fed predator.[10] Keep the temperature within the species' range and stable rather than at the very top of it, since warmer water holds less oxygen.[7]

  5. Plan for the adult size

    If the arowana is outgrowing its tank, the only lasting solution is a much larger aquarium or a pond. A fish that can swim freely jumps less from stress, and keepers report the difference is dramatic once an arowana has real space.[6] Until then, keep tankmates calm and avoid anything that harasses the arowana.

Preventing Jumping Injuries in Silver Arowana

Assume every silver arowana will jump, from the day it arrives, and fit a heavy, sealed lid before the fish goes in.[6] Feed from the surface without putting your hand over the open water, and keep feeding times regular so the fish is not constantly on alert. Keep the water clean and well oxygenated,[7][10] choose calm tankmates, and give the fish room to grow — adults reach about 90 cm.[4] Quarantine new fish before adding them so parasites are not introduced into the arowana's tank.

When a Jumping Arowana Needs Expert Help

Emergency: if the arowana has been found out of the water, return it immediately; a fish that has been out for long, is lying on its side, has bleeding from the mouth or gills, or does not swim normally within an hour has likely suffered internal injury and needs a veterinarian who treats fish. Act within a day or two if: it has wounds, split lips, lifted scales or cloudy eyes after hitting the lid, because skin breaks let infections in.[8] Also get help if jumping comes with fast breathing, flashing or loss of appetite, which point to water quality or parasites rather than normal hunting.[7][9] Drooping eyes ("drop eye") are a separate condition and not an emergency.

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Frequently Asked Questions

Is it normal for a silver arowana to jump?
Yes. In the wild silver arowana leap out of the water to catch insects, spiders and small vertebrates from overhanging branches,[1][5] and jumping for food is part of the species' normal biology.[4] It becomes a problem only when the tank is not covered or when the fish is jumping from fright or poor water.
How high can a silver arowana jump?
Keepers and aquarium writers describe wild arowana leaping up to about four feet (over a metre) to take prey from branches.[6] Even a juvenile can clear a tank rim easily, which is why an open-topped tank is never safe for this species.
My arowana jumped out of the tank and looks dead. What should I do?
Put it back in the tank immediately, even if it looks lifeless, and hold it upright in front of the filter outlet so water flows over the gills. Some fish recover after short periods out of water. Keep the lights off, keep the water clean and watch for infection at any wounds over the next week,[8] and contact a fish vet if it cannot swim normally.
Does jumping cause drop eye in arowana?
Nobody knows for certain. Drop eye — where one or both eyes turn permanently downward — is common in captive arowana, and suggested causes include inbreeding, a fatty diet and constantly looking down at food or activity below the tank.[6] Affected fish can still live a full lifespan, so it is a cosmetic concern rather than an emergency.[6]
Will my arowana stop jumping as it gets older?
Not reliably. Adults hunt the same way juveniles do,[1] and a larger fish that jumps is more likely to hurt itself. Jumping from fright does usually decrease once the fish has settled and has enough space, but the lid needs to stay on for the fish's whole life.
Why does my arowana jump when I turn the light on?
A sudden change from dark to bright light startles many fish, and light is a recognised stressor.[8] Arowana react to fright by leaping, which is when most serious injuries happen.[6] Switch the room light on first, or use a tank light with a slow sunrise setting.
✓
Editorial review

This guide was researched against the veterinary and scientific sources listed below and reviewed for biological accuracy. Test water parameters before treating a sick fish, and consult an aquatic veterinarian if symptoms persist after 48 hours of correct treatment.

References

  1. Lowry, D., Wintzer, A.P., Matott, M.P., Whitenack, L.B., Huber, D.R., Dean, M. & Motta, P.J. (2005). Aerial and aquatic feeding in the silver arawana, Osteoglossum bicirrhosum. Environmental Biology of Fishes 73(4): 453–462. doi:10.1007/s10641-005-3214-4
  2. Freitas, P.H.L. de, Bussons, M.R.F.M., Bussons, I.N.B., Dias, F.V.N., Garcês, L.M., Sousa, E.S. & Oliveira, A.T. de (2025). Feeding Ecology of Osteoglossum bicirrhosum (Osteoglossiformes: Osteoglossidae) in a Central Amazon Reserve. Anais da Academia Brasileira de Ciências 97(2): e20241121. doi:10.1590/0001-3765202520241121
  3. Verba, J.T., Lima de Oliveira Borges, M., Ferreira da Silva, M.N., Costa Pinto, L. & Rabello Neto, J.G. (2018). Mice on menu: opportunistic feeding behaviour of the Amazonian silver arowana Osteoglossum bicirrhosum. Journal of Fish Biology 93(1): 132–133. doi:10.1111/jfb.13665
  4. U.S. Fish and Wildlife Service (2017). Arawana (Osteoglossum bicirrhosum) Ecological Risk Screening Summary. U.S. Fish and Wildlife Service, revised August 2017. fws.gov
  5. Birchmeier, K. (2000). Osteoglossum bicirrhosum (Arawana). Animal Diversity Web, University of Michigan Museum of Zoology. animaldiversity.org
  6. Lim, T.K.L. The South American Silver Arowana. Tropical Fish Hobbyist Magazine. tfhmagazine.com
  7. Merck Veterinary Manual. Environmental Diseases of Aquatic Animals in Aquatic Systems. Merck & Co., Inc. merckvetmanual.com
  8. Francis-Floyd, R. Stress—Its Role in Fish Disease. UF/IFAS Extension, Circular 919 (FA005). edis.ifas.ufl.edu
  9. Merck Veterinary Manual. Disorders and Diseases of Fish. Merck & Co., Inc. merckvetmanual.com
  10. Francis-Floyd, R., Watson, C., Petty, D. & Pouder, D.B. (2022). Ammonia in Aquatic Systems. UF/IFAS Extension, FA16. doi:10.32473/edis-fa031-2022