One of the largest true freshwater fish in the world, native to the Amazon basin. Arapaima are obligate air-breathers and extreme predators. Due to their massive adult size and explosive growth rate, they are almost entirely unsuited for home aquaria and require highly specialized, heated, pond-sized enclosures.
Arapaima At a Glance
Arapaima Tank Requirements
Will Arapaima fit in your tank?
Care guides tell you what Arapaima needs, the next question is whether your tank can safely provide it. Test Arapaima against your tank size, maintenance needs, and the fish you already keep before you buy.
Arapaima Water Parameters
Arapaima Temperament & Compatibility
Arapaima Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Adult / Standard
The fully grown form. Requires heavily reinforced, custom-built pools or public aquarium facilities. Will consume any fish that fits into its cavernous mouth. Prone to fatal injuries if they jump and hit hard lids or walls.
Differs in 1 trait from base species
Also known as: Adult Pirarucu, Full Grown
Juvenile (Grow-out)
Often sold in the trade at 15-25cm. Do not be fooled: they have an explosive growth rate, often reaching over 1 meter (100cm+) in their first year alone. A 750L tank is only a temporary staging ground for a few months.
Differs in 4 traits from base species
Also known as: Baby Arapaima, Juvenile
Arapaima Care Guide Summary
The Arapaima, scientifically known as Arapaima gigas, belongs to the Oddballs family group. Adults reach a maximum size of approximately 300 cm and have a fusiform body shape with a fast growth rate. Classified as aggressive, this species primarily occupies the surface and mid-level zones of the aquarium and produces a extreme level of biological waste.
To thrive, the Arapaima requires a freshwater only aquarium with a minimum volume of 15000 litres and a tank length of at least 600 cm. Water temperature should be maintained between 24°C and 30°C, with a pH range of 6–7.5 and a general hardness of 2–15 dGH. A low water flow is preferred.
Due to its specialist needs, the Arapaima is best suited for fishkeepers who can provide a carefully planned setup. This species is available in 2 varieties: Adult / Standard and Juvenile (Grow-out). Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Arapaima Habitat Setup
When setting up an aquarium for the Arapaima, a low water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper and live planted layouts may be difficult to maintain, as this species tends to uproot or consume vegetation.
Arapaima Compatibility Notes
Classified as aggressive, the Arapaima is adaptable and can be kept singly or in a small group, offering flexibility when planning a community tank. When choosing tankmates, any fish small enough to fit in its mouth will likely be eaten, conspecific aggression can be intense, especially in smaller tanks, and their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Who Arapaima Is Actually For
Arapaima is best for a fishkeeper who expects a species with attitude and plans the tank around that behavior and can provide someone who understands its individual space requirements. It suits keepers who want a profile-driven species choice without a long list of specialist setup demands.
The most common mistake is buying Arapaima for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is forcing it into an over-busy community when it would do better with more room or more deliberate tankmate choices.
Frequently Asked Questions About Arapaima
How big does Arapaima get?
Arapaima (Arapaima gigas) typically reaches a maximum adult size of approximately 300 cm. They have a fusiform body shape and a fast growth rate.
What tank size does Arapaima need?
A minimum aquarium volume of 15000 litres and a tank length of at least 600 cm are recommended for Arapaima. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Arapaima need?
Arapaima thrives in freshwater only conditions with a temperature range of 24–30°C, a pH between 6 and 7.5, and a general hardness of 2–15 dGH. A low water flow is preferred.
Is Arapaima peaceful or aggressive?
Arapaima is classified as aggressive with an aggression score of 7 out of 10. Careful tankmate selection is essential to avoid conflict.
Can Arapaima live alone?
Yes, Arapaima can be kept singly or in a group. They are flexible and adapt well to both setups.
Does Arapaima need a lid on the tank?
Yes. Arapaima is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- May 1, 2026
- Last updated
- May 1, 2026
- Issues or corrections?
- Contact the editorial team
Plants That Suit Arapaima
These plants pair well with Arapaima based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Banana Plant
Nymphoides aquatica
Beckett's Water Trumpet
Cryptocoryne beckettii
Broad-leaved Crypt
Cryptocoryne pontederiifolia
Crypt Wendtii
Cryptocoryne wendtii
Fish Similar to Arapaima
Piraiba
Brachyplatystoma filamentosum
One of the largest freshwater fish in the world, native to the Amazon Basin. It is a highly active, migratory apex predator. This 'Monster Fish' is almost entirely unsuitable for home aquaria, requiring an enormous, custom-built heated indoor pool or public aquarium setting for its adult life stage.
Pacific Sturgeon
Acipenser transmontanus
The Pacific (or White) Sturgeon is the largest freshwater fish in North America. As a true 'monster fish', it requires an absolutely massive indoor facility or an outdoor pond. They are coldwater, anadromous fish that require high oxygen levels, fast flow, and a soft sandy substrate to protect their sensitive sensory barbels. They are strict bottom feeders and will inadvertently swallow small tank mates.
Dourada
Brachyplatystoma rousseauxii
The Dourada is a truly massive, highly predatory migratory catfish native to the Amazon and Orinoco basins. Known for its silvery-gold sheen and the longest freshwater migration of any fish in the world. In captivity, it is a 'monster fish' that requires a massive custom aquarium or indoor pond. It is exclusively piscivorous and will swallow any fish that fits in its immense mouth.
Pungas Catfish
Pangasius pangasius
A colossal riverine catfish native to the Indian subcontinent. While highly important for aquaculture, they are disastrous for home aquariums. They grow rapidly to enormous sizes (up to 150-300cm), are easily spooked (often resulting in them ramming the tank glass at high speeds), and will swallow any tank mate that fits in their massive mouths.
Helicopter Catfish
Wallagonia leerii
A massive, apex predator catfish native to Southeast Asia. Known for its enormous mouth and voracious appetite, this 'monster fish' is completely unsuitable for standard home aquariums. In the wild, they migrate through large rivers and flooded forests. They will consume any tankmate that fits in their massive mouth. Kept almost exclusively by specialized monster fish keepers or public aquaria.
Indonesian Giant Snakehead
Channa micropeltes
One of the largest, most aggressive, and predatory freshwater fish in the world. The Giant Snakehead is an apex predator equipped with a labyrinth organ, allowing it to breathe atmospheric air. In captivity, they require massive, heavily secured indoor ponds or custom ultra-large aquariums. They possess crushing jaw strength and will consume or brutally attack almost any tank mate.