What an Arowana Is and Why It Matters

An arowana is a large, predatory freshwater fish native to South America, Southeast Asia, and Australia. The fish can grow 24 to 48 inches long depending on the species, with a streamlined body, large scales, and a distinctive barbel (whisker-like sensory organ) hanging from its lower jaw. Arowanas are aggressive hunters that eat smaller fish, shrimp, and insects in the wild, and they demand considerably more space and care than most home aquarium fish.

If you are considering an arowana, you need to understand upfront that this is not a beginner fish. The species requires a tank of at least 150 gallons for a single adult, strict water parameters, live or frozen food, and a commitment to 15 to 20 years of care. Many people buy arowanas on impulse because they look striking, then struggle when the fish outgrows a standard tank or becomes aggressive toward tank mates.

Key Takeaways

  • Arowanas need a minimum 150-gallon tank and can live 15 to 20 years, making them a long-term commitment that requires planning before purchase.
  • The fish are carnivorous and will eat smaller fish and invertebrates, so tank mates must be large enough not to trigger predatory behavior.
  • Water temperature should stay between 72 and 82 degrees Fahrenheit, with neutral to slightly acidic pH and regular partial water changes to maintain water quality.
  • Some arowana species are protected or restricted by law in certain regions, so check local regulations before buying one.

Tank Size and Setup Requirements

A single adult arowana requires a minimum of 150 gallons, though 200 gallons or larger is preferable because it gives the fish room to move and reduces stress-related aggression. The tank should be longer than it is tall—a 6-foot by 2-foot by 2-foot setup works better than a tall, narrow one, because arowanas are horizontal swimmers and need length to patrol.

The tank must have a secure, tight-fitting lid. Arowanas are powerful jumpers and will launch themselves out of the water if startled or pursuing food. A standard aquarium hood is not enough; you need a lid that clamps down or fits snugly enough that the fish cannot dislodge it. Substrate can be sand or fine gravel, and décor should include driftwood or rock formations that provide hiding spots without creating sharp edges that could damage the fish's scales.

Filtration is critical. Use a canister filter rated for at least 10 times the tank volume per hour—so for a 150-gallon tank, aim for 1,500 gallons per hour of flow. Arowanas produce substantial waste, and poor water quality leads to disease and aggression. Perform 25 to 30 percent water changes every week to keep nitrate levels low.

Water Conditions and Temperature Control

Arowanas thrive in warm water between 72 and 82 degrees Fahrenheit. A reliable aquarium heater is essential, especially if your home temperature fluctuates. Use a heater rated for your tank size—for a 150-gallon tank, a 300-watt heater is a reasonable starting point, though you may need to adjust based on your room temperature and how quickly the heater maintains the set point.

pH should be neutral to slightly acidic, between 6.0 and 7.0. Hardness is less critical, but soft to moderately hard water (4 to 8 dGH) mimics the fish's natural habitat. Test water parameters weekly with a reliable kit or meter. Ammonia and nitrite must always be zero; nitrate should stay below 40 ppm. If nitrate climbs above that, increase water change frequency or reduce feeding.

Feeding and Diet

Arowanas are carnivores and will not eat flake food or pellets designed for omnivorous fish. Feed live or frozen food: small fish (feeder fish, silversides, or smelt), shrimp, insects (crickets, grasshoppers), or earthworms. Many keepers rotate between frozen options to provide variety and reduce the risk of parasites that can come with live feeder fish.

Feed juveniles once or twice daily, and adults once daily or every other day, depending on the fish's size and activity level. Overfeeding leads to obesity and poor water quality. A good rule is to feed an amount the fish can consume in a few minutes. Watch the fish's body shape—it should have a slight curve to its belly, not a bulge. Frozen food should be thawed in tank water before feeding to avoid temperature shock.

Temperament and Tank Mates

Arowanas are solitary, territorial hunters. They will eat any fish small enough to fit in their mouth, and they may attack or harass larger fish that compete for space or food. Housing an arowana with other fish is risky and requires careful planning. Tank mates must be large (6 inches or longer), fast-moving, and not aggressive themselves—large plecos, large catfish, or large cichlids are sometimes kept with arowanas, but even these pairings can fail if the arowana becomes territorial.

Many experienced keepers keep arowanas alone. A single arowana in a well-maintained 150-gallon tank is healthier and less stressed than one forced to share space. If you want a community setup, an arowana is not the right choice.

Species Variations and Legal Restrictions

The most common species in the aquarium trade are the silver arowana (South American), the black arowana (South American), and the Asian arowana (Southeast Asian). The Asian arowana, particularly the red and gold varieties, is highly prized but also expensive and restricted by law in many countries. Some Asian arowana species are listed under CITES (Convention on International Trade in Endangered Species), meaning they require special permits to own, transport, or sell.

Before buying any arowana, check your local and regional regulations. Some countries and states prohibit Asian arowanas entirely, while others require a permit. Some municipalities restrict tank size or have rules about keeping large predatory fish. Violating these laws can result in confiscation of the fish and fines. Contact your local fish and wildlife agency or aquarium club to confirm what is legal in your area.

Common Health Issues and Prevention

Arowanas are hardy if water conditions are stable, but they are susceptible to several problems. Poor water quality causes bacterial infections, fin rot, and scale damage. Stress from inadequate tank size or aggressive tank mates leads to disease and behavioral problems like refusing food or jumping. Parasites can enter through live feeder fish, so quarantine live food or use frozen alternatives.

Watch for signs of illness: torn fins, white spots or patches on the body, loss of appetite, or erratic swimming. If you notice these signs, perform a large water change immediately and check all water parameters. If the problem persists, consult a veterinarian who has experience with large fish. Antibiotics and other treatments designed for small community fish often do not work on large predators like arowanas.

Cost and Long-Term Commitment

The initial setup for an arowana is expensive. A 150-gallon tank, stand, canister filter, heater, and lighting can easily cost $1,500 to $3,000 before you buy the fish itself. Silver arowanas typically cost $50 to $150, while Asian arowanas can cost $500 to several thousand dollars depending on color and origin. Ongoing costs include electricity for heating and filtration, food, water treatments, and occasional equipment replacement.

Beyond money, arowanas demand time. Weekly water changes, daily feeding, and regular observation are non-negotiable. If you travel frequently or cannot commit to this routine, an arowana is not a good fit. The fish can live 15 to 20 years in captivity, so you are making a commitment that may outlast your interest in the hobby.

Frequently Asked Questions

Can I keep an arowana in a 75-gallon tank?

No. A 75-gallon tank is too small for an adult arowana. The fish will become stressed, aggressive, and prone to disease. Minimum tank size is 150 gallons for a single adult, and larger is better. Juveniles can start in smaller tanks, but they grow quickly and will need to be moved to a larger setup within a year or two.

What do I feed an arowana if I do not want to use live fish?

Frozen food is a good alternative. Silversides, smelt, shrimp, and earthworms are all available frozen at aquarium stores or online. Thaw the food in tank water before feeding. Some keepers also use large pellets or sticks designed for carnivorous fish, though arowanas may be picky about non-living food and may need live or frozen options to maintain appetite.

Can I keep two arowanas together?

Not reliably. Arowanas are territorial and will fight if confined together, even in large tanks. Two arowanas require separate tanks. Some breeders keep juveniles together temporarily, but they must be separated as they grow. A single arowana is the safest and most humane option.

Do arowanas need a special permit to own?

It depends on your location and the species. Silver and black arowanas are generally legal in most places, but Asian arowanas are restricted or banned in many countries and states. Check with your local fish and wildlife agency or aquarium club before buying. Owning a restricted species without a permit can result in confiscation and fines.

How often should I do water changes?

Perform a 25 to 30 percent water change every week. Arowanas produce a lot of waste, and regular water changes are essential to keep nitrate and other waste products under control. If you skip water changes or do them infrequently, water quality will decline and the fish will become stressed and sick.