Juvenile (4–8 inches, 0–6 months)
A juvenile arowana fits comfortably in a 75-gallon (4 ft × 18 in × 18 in) tank for the first 4–6 months. Use sponge filtration, weekly 25% water changes, and a tight lid.
Even at this size, jumping is a risk. Always keep the lid on, and feed with the lid only briefly cracked.
Sub-adult (8–18 inches, 6–18 months)
By 8 inches, plan the move to 180–250 gallons (6 ft × 24 in × 24 in). Growth accelerates dramatically with feeding 2–3 times per day. The fish can outgrow a 75-gallon in 3 months at this stage.
Filtration must scale up. A 180-gallon arowana tank needs at least 2× canister filters or a sump.
Adult (18–30+ inches, 18 months onward)
A fully grown silver, asian, or jardini arowana needs a 250–400+ gallon tank with 8-foot minimum length. This is permanent housing — there is no "next upgrade" beyond this.
A 96″ × 30″ × 24″ tank holds 300 gallons and is the practical sweet spot. Custom builds reach 600+ gallons for breeding pairs or community setups.
Cost Reality
A 250-gallon tank, stand, lid, filtration, heater, and lighting setup costs $1,500–4,000 new. A custom 8-foot acrylic tank is $3,000–8,000.
Budget $50–100/month for food, $30–50/month for water and electricity, and $200/year for filter media. Total 5-year cost of ownership: $5,000–15,000.