Arowana companions must be assessed against the exact species, adult mouth size, temperament and available space. A fish being large today does not guarantee safety after the predator grows. Solitary housing is often simpler than maintaining a mixed giant-fish display.
Begin with the arowana care guide and plan the adult aquarium first. Other residents add their own footprint, social needs and waste. A 75-gallon aquarium is not a mixed adult-arowana setup, regardless of how well small juveniles appear to fit.
1. Clown loach: adults and a proper group only
Clown loaches need a social group, shelters and directly supplied food. Small shop juveniles can become prey. Plan their full adult size and verify temperature compatibility; not all arowanas come from Southeast Asia or share identical conditions.
2. Flowerhorn: aggression makes this a poor default pairing
A flowerhorn can injure an arowana’s flanks and fins. Large scales do not prevent damage, and different swimming levels do not create separate aquariums. Shared popularity in the ornamental trade says nothing about compatibility.
3. Silver dollars: identify the species and provide the shoal
Silver dollars can be plausible companions in a sufficiently large installation, but adults must be too large to swallow and have their own group swimming space. Smaller species, juveniles and larger red-hook relatives are not interchangeable. Supply their plant-containing diet separately from the arowana’s food.
4. Oscar: watch territory as well as size
An oscar is a substantial cichlid with its own adult footprint and waste load. Some individuals coexist with arowanas; others harass them or suffer stress themselves. Neither species needs petting or hand-feeding for successful care. Use feeding and resting behavior to assess the pairing.
5. Black ghost knifefish: protected feeding is essential
Apteronotus albifrons is a large but relatively timid fish. Its species profile recommends a 180 × 60 cm adult aquarium base. Provide refuges and food where it can eat, often under dim light. A small specimen may be swallowed, while a larger one can still be outcompeted.
6. Freshwater stingray: a separate specialist commitment
Freshwater rays require species-specific floor area, exceptional water management and safe maintenance around their venomous spine. The motoro profile lists adults around 50 cm across the disc and a 240 × 90 cm base. That is not a blanket size recommendation for every ray-and-arowana combination.
7. Red-tail catfish: usually reject this suggestion
A red-tail catfish grows enormous and may swallow large companions. Raising it beside an arowana does not guarantee matching growth rates or safety. It belongs in a suitably designed giant installation, not a home aquarium selected around a juvenile arowana.
8. Severum: a conditional cichlid option
An adult severum may be suitable with some arowanas, but it is not automatically too large to eat. Check body size, water requirements and breeding territory. Juveniles remain vulnerable, and spawning pairs may displace other residents.
9. Green terror: compare temperature and territoriality
Andinoacara rivulatus can become strongly territorial. Its species profile gives a cooler 20–24°C care range, which may conflict with the intended arowana setup. A green fish contrasting with a silver fish is an aesthetic observation, not a stocking criterion.
10. Fire eel: sheltered does not mean protected
Mastacembelus erythrotaenia becomes a very large fish requiring its own adult footprint, suitable substrate, refuges and escape-proof gaps. Feed it directly rather than assuming it catches scraps. Small eels may become prey and larger ones can still suffer harassment or feeding competition.
Rules for any attempted combination
Quarantine newcomers, compare the intended water conditions and have an established separation aquarium available. Watch every resident eat. Reassess as fish grow, and separate them if pursuit, injuries, constant hiding or missed meals occur. A video of a successful combination does not establish a safe lifelong stock list.
