Before You Buy: The Honest Reality
An arowana is a 10–15 year, 24–36 inch commitment. The tank you need is a 250+ gallon (8-foot minimum length) custom build with a tight, weighted lid. The food bill alone runs $30–80 per month. And once your fish hits 18 inches, rehoming becomes nearly impossible.
Asian arowanas (Scleropages formosus) require CITES paperwork and a microchip in many countries. Silver arowanas (Osteoglossum bicirrhosum) are legal everywhere and far cheaper, but grow just as large.
If any of those facts make you hesitate, buy a different fish. Arowanas suffer when downsized to "just for now" tanks — bent spines, drop eye, and shortened lifespans are the price.
Tank Size and Layout
Arowanas are surface predators. They patrol the top third of the tank in long horizontal sweeps, often colliding with glass when startled. The tank length must equal at least 3× the adult body length. For a 30-inch silver arowana, that means a 90+ inch tank — roughly 8 feet.
Width matters more than depth. A 96″ × 30″ × 24″ tank holds the same water as 96″ × 24″ × 30″, but the wider footprint lets the fish turn without scraping. Aim for at least 24 inches of width.
Keep décor minimal: no sharp rocks, no spiky driftwood, no tall plants near the surface. Arowanas damage their barbels and gill covers on hard décor. A bare bottom or fine sand is best.
- ✦Minimum 250 gallons — 400+ for a fully grown adult
- ✦8-foot length is the practical minimum
- ✦Cover the lid with weight (10+ kg) — arowanas jump and break thin glass tops
- ✦Avoid overhead lights that cast strong shadows — sudden shadows trigger panic jumps
Water Parameters
Arowanas come from soft, warm, slightly acidic Amazon (silver) or Southeast Asian (Asian) waters. They tolerate a wide range, but stability matters more than chasing exact numbers.
Run a powerful canister or sump filter rated for 2× the tank volume per hour. Arowanas are messy carnivores producing huge waste loads. Weekly 30–40% water changes are non-negotiable.
- ✦Temperature: 78–86°F (26–30°C) — heated, never let it drop
- ✦pH: 6.5–7.5 — soft, slightly acidic preferred
- ✦Ammonia and nitrite: 0 ppm always
- ✦Nitrate: keep under 20 ppm — this is the parameter that fails first
Diet — Live, Frozen, or Pellet?
Adult arowanas accept high-quality floating pellets (Hikari Massivore, NLS Jumbo Predator) as a staple, but they need protein variety. Frozen krill, silversides, prawns, and earthworms cover micronutrients.
Avoid feeder goldfish and rosy reds — they carry parasites and contain thiaminase, which damages the arowana liver and shortens lifespan dramatically.
Feed juveniles 2–3 times daily, sub-adults once daily, adults every 2–3 days. Overfeeding causes the gut to bulge and the fish to lose its sleek hunting profile.
- ✦Pellets: convenient, balanced, but vary brands
- ✦Crickets and grasshoppers: excellent natural prey
- ✦Shrimp (whole, shell on): fiber and color enhancement
- ✦No feeder fish — disease + thiaminase risk
Drop Eye and How to Prevent It
Drop eye is the single most common cosmetic defect in captive arowanas. The eye angles permanently downward, ruining the show value of the fish.
The cause is debated, but the consensus among breeders points to: tanks that are too short (forcing the fish to look down), bright overhead lighting, and floating food that the fish learns to chase along the surface (training the eye downward).
Prevention: ensure the tank is at least 30 inches wide so the fish can swim mid-water comfortably, dim or remove overhead lighting, use sinking pellets occasionally, and float ping-pong balls on the surface to obstruct downward sight lines.
Tank Mates
Arowanas are best kept solo or with very large, peaceful companions in massive tanks. Common compatible species include large datnoids, peacock bass, freshwater stingrays, large plecos (in 500+ gallon tanks), and giant gouramis.
Never mix with cichlids small enough to be eaten or aggressive enough to fin-nip. Avoid all bottom-dwelling fish that compete for territory under the arowana — flowerhorns, oscars, and large barbs are problematic.
Two arowanas in one tank rarely works long-term. They establish dominance and the loser stops eating.