Best Tank Mates for Arowana: Compatible Fish and Species to Avoid
The best tank mates for arowana are large, sturdy fish that live in the middle or bottom of the tank and will always be too big to swallow. Good examples are large plecos, bichirs, silver dollars, datnoids and robust catfish. Tetras, goldfish, angelfish and anything that stays small get eaten. Below you'll find what works, what doesn't, and how to introduce new fish without losing any.
Start With the US Reality: Which Arowana Do You Have?
In the United States, most hobbyists can only legally buy silver, black, or Australian (jardini or leichardti) arowanas. The Asian arowana is protected under the Endangered Species Act and is illegal to buy, own, or move across state lines. So this guide sizes every recommendation against the fish most US keepers actually own: a silver arowana that will reach about 3 ft (90 cm) as an adult.
Legal limits also apply to tank mates. Snakeheads are federally listed as injurious wildlife and banned in many states, and some states regulate other large exotic fish. Check your state's rules before buying any "monster fish."
The Three Rules of Arowana Compatibility
1. Plan around mouth gape, not current size
A tank mate has to stay too big to swallow for the arowana's entire life. Young arowanas can grow about 2 in (5 cm) a month, so a fish that's safe today can be dinner 4–6 months from now. Arowanas have a very wide upturned mouth. Judge a tank mate by the arowana's adult gape, not the 6 in (15 cm) juvenile in front of you. A good working rule is that new fish should be at least about half the arowana's length and clearly deeper-bodied than its mouth.
2. Leave the surface to the arowana
Arowanas are surface hunters, and they treat the top few inches of water as their territory. Choose mid-water and bottom-dwelling fish so nobody competes for that space. Surface-level fish, and fish that dart up to grab food at the top, cause the most fights.
3. Pick sturdy, not scrappy
The right companion can shrug off an occasional snap without becoming a bully. Skip fin-nippers and highly territorial fish. They either shred the arowana's long fins or stress it into lunging and jumping.
Are Arowanas Aggressive?
Yes. Arowanas are predators that eat anything that fits in their mouths, and they get more aggressive as they grow. How aggressive depends on the species:
- Australian (jardini/leichardti): the most aggressive. Many won't accept any tank mates once they reach about 12–14 in (30–35 cm).
- Silver: the mildest, and the best choice for a community.
- Black: similar to silver, but can be more territorial.
- Asian: territorial as well, though not legal for US hobbyists.
Several things make aggression worse: stress, poor water quality, underfeeding, a cramped tank, and breeding behavior (males brood eggs in their mouths). Expect lunging or biting at hands during feeding and maintenance, too.
Tank Size and Water Conditions
A community around an arowana needs more room than the arowana alone.
- Adult silver or black: 250+ gallons (950+ L), 8–10 ft (2.4–3 m) long, and more than 2.5 ft (75 cm) front to back so it can turn around.
- Juveniles: a 75–125 gallon (285–475 L) tank works as a temporary grow-out, not a permanent home.
- Lid: heavy and tight-fitting. Arowanas are well-known jumpers.
Advice on minimum tank size varies a lot, from 75 gallons (with a single flowerhorn) up to 250 gallons and 8–10 ft for a full community. Our recommendation: treat 75–125 gallons as grow-out only and plan on 250+ gallons permanently.
| Parameter | Target |
|---|---|
| Temperature | 76–84°F (24–29°C) |
| pH | 6.0–7.0 |
| Hardness | Soft to moderately hard |
| Nitrate | Below about 20 ppm |
| Filtration | Rated for 5–10x tank volume per hour |
| Water changes | 25–30% weekly |
A tank with a big predator and several large companions produces a lot of waste. Undersized filtration is a common cause of drop eye, fin rot and extra aggression. Oversize your filtration from day one.
Best Tank Mates for Arowana
Bottom dwellers
- Large plecos (common, sailfin): armored, tough, and out of the way. Add them when they're already a good size.
- Raphael and other doradid catfish: spiny, armored and nearly impossible to swallow.
- Ornate or Senegal bichirs: prehistoric-looking bottom fish that hold their own. Browse bichirs and other bottom dwellers to see current options.
- Clown loaches: only as a group of 5 or more (see the caveat below).
- Black ghost knifefish: nocturnal and peaceful, and grows long enough to be safe.
- Freshwater stingrays: a classic pairing, but for experts only because they need pristine water.
Mid-water fish
- Silver dollars: in schools of 6 or more. They're deep-bodied and fast.
- Tinfoil barbs: large, active schooling fish.
- Bala sharks: keep them in groups. They grow big enough to be safe.
- Siamese tiger or Indo datnoids: calm ambush predators that stay in the middle levels. Some datnoid species do better in slightly brackish or harder water, so choose freshwater-tolerant species.
- Giant gourami: huge and slow-moving.
- Clown knifefish: a large, mostly nocturnal predator with a similar temperament.
Cichlids (very large tanks only)
Oscar, severum, green terror, Jack Dempsey, Texas cichlid, jaguar cichlid and flowerhorn can work, but only in very large tanks and with close watching. Cichlids claim territory on the bottom and can harass a timid silver. The problem can run both ways.
Quick compatibility reference
| Fish | Tank zone | Verdict | Key note |
|---|---|---|---|
| Common/sailfin pleco | Bottom | Good | Add at a large size |
| Ornate/Senegal bichir | Bottom | Good | Feed sinking food separately |
| Silver dollar | Mid | Good | School of 6+ |
| Tinfoil barb | Mid | Good | Needs swimming room |
| Siamese tiger datnoid | Mid | Good | Pick freshwater-tolerant species |
| Clown loach | Bottom | Conditional | Big group, big tank, no jardini |
| Oscar/flowerhorn | Bottom–mid | Conditional | 250+ gal, watch closely |
| Stingray | Bottom | Experts only | Pristine water required |
| Red tail catfish | Bottom | Avoid | Can swallow the arowana |
| Tetras, guppies | All | Avoid | Eaten |
Species to Avoid
Fish that become food
- Tetras, guppies and other small community fish. They get eaten.
- Goldfish. They're coldwater fish and make poor feeders.
- Angelfish and discus. They're easy to eat and stress easily.
- Pearl gouramis and other small gouramis.
- Small cichlids like firemouths and blood parrots, plus flying foxes. These sometimes show up on compatibility lists, but they end up bite-sized. Skip them.
- Anything under about 6 in (15 cm) as an adult.
Giants that don't belong in home tanks
Some lists recommend these big fish, but we advise against all of them:
- Red tail catfish reach 3–5 ft (90–150 cm) and can swallow the arowana.
- Pacu and iridescent sharks need pond-sized space. Iridescent sharks also panic and crash into the glass.
- Peacock bass outgrow the same tank the arowana needs.
- Snakeheads are federally listed injurious wildlife and illegal in many states.
The clown loach caveat
Most keepers rate clown loaches as good bottom companions, but loaches can get stressed around aggressive fish. Keep them only as a large, confident group in a big tank, and don't add them to a jardini setup.
Can You Keep More Than One Arowana?
Some keepers report success with multiple arowanas in 240+ gallons, but most find them very intolerant of their own kind. The safe approach is one arowana, or a group of 5 or more only in a huge setup so aggression is spread out. Never keep a pair. One fish usually harasses the other until it's badly hurt.
How to Introduce Tank Mates Safely
- Quarantine every new fish for 2–4 weeks in a separate tank.
- Add tank mates at the same time as a juvenile arowana, or before it. Adding fish to an adult's established territory is the riskiest option.
- Rearrange the decor right before adding anyone so old territories are broken up.
- Feed well before and during the introduction.
- Watch closely for the first 1–2 weeks.
- Have an exit plan: a backup tank or a tank divider ready before you need it.
After that, keep the arowana well fed. A hungry arowana is more aggressive and more likely to go after tank mates. Feed bottom dwellers separately with sinking food so they aren't competing at the surface.
Sample Stocking Plans
- 250 gallons: 1 silver arowana, 6 silver dollars, 1 common pleco, 2 ornate bichirs.
- 300+ gallons: the same, plus a datnoid and a clown knifefish.
Both plans put the arowana alone at the surface, a school in the middle, and armored or bottom-hugging fish below.
Common Mistakes and Troubleshooting
- Buying tank mates sized for today's juvenile. A fish that fits a 6 in (15 cm) arowana can disappear once it reaches 18 in (45 cm).
- Dropping a new fish into an established territory without changing the decor.
- Keeping surface feeders that steal food and start fights at the top.
- Too little filtration for a heavy predator load.
| Symptom | Likely cause | Fix |
|---|---|---|
| Fish missing overnight | Tank mate small enough for the arowana's gape | Rehome remaining small fish, stock larger |
| Torn fins | Nipping or territorial cichlid | Remove or divide off the culprit |
| Jumping or scraped scales | Open lid, stress, bright lights | Secure the lid, add floating plants or cover, dim lights at feeding |
| Cloudy eyes, fin rot, rising aggression | Poor water, weak filtration | Increase filtration and water changes, test nitrate |
Frequently Asked Questions
Can arowanas live with other fish?
Yes, if the tank mates are large, sturdy and stay in the lower part of the tank. Silver and black arowanas are the most accepting. Australian jardini are often best kept alone.
Can two arowanas live together?
Rarely. Arowanas are intolerant of each other, and pairs usually end with one fish injured. Keep a single arowana, or a group of 5 or more only in a very large tank.
Can arowana live with Oscars or flowerhorns?
Sometimes, in tanks of 250+ gallons (950+ L). Watch both fish, because the aggression can run either way. A flowerhorn may bully a timid silver just as easily as the arowana may snap at it.
Will an arowana eat a pleco?
A small one, yes. Adult large plecos such as common or sailfin plecos are generally safe because of their size and armor. Add them once they're already big.
What are the best schooling fish for an arowana tank, and how big should tank mates be?
Silver dollars, tinfoil barbs and bala sharks, kept in groups, are the top choices. Any new tank mate should be at least about half the arowana's length and larger than its mouth.
Should I feed my arowana feeder fish?
No. Feeder fish can carry disease into the tank, and they teach the arowana that small fish are food, which puts your tank mates at risk. Stick to prepared and frozen foods.
Build Your Arowana Community
A peaceful arowana tank comes down to planning for adult sizes, keeping the surface to the arowana, and choosing tough companions for the lower levels. When you're ready to stock, browse robust species in the Monster Fishes collection on FishyHub.
