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.
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Arapaima Water Parameters
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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.
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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.
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
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.
Red-Tail Catfish
Phractocephalus hemioliopterus
A massive, fast-growing predatory catfish from the Amazon basin. Famous for its voracious appetite, bulldozer-like behavior, and distinct red caudal fin. Due to its enormous adult size (often exceeding 4 feet), it is strictly a 'monster fish' that requires a heated indoor pond or a colossal custom aquarium. It is highly predatory and will swallow absolutely any tank mate that can fit into its cavernous mouth.
Freshwater Shark (Wallago)
Wallago attu
An apex predator native to South and Southeast Asia, infamous for its immense size, huge mouth, and voracious predatory nature. It will consume any tank mate that fits into its capacious mouth and is known to bite aggressively when handled. This species is utterly unsuitable for standard home aquariums and requires an enormous custom pond or public aquarium setup.
Chao Phraya Giant Catfish (Paroon Shark)
Pangasius sanitwongsei
An apex predator native to the Mekong and Chao Phraya basins. This true 'monster fish' is completely unsuitable for home aquariums. They grow to massive proportions, are highly active, and easily startled—often severely injuring themselves by crashing into tank walls. They possess a massive appetite and are highly piscivorous, consuming any tank mate that fits in their mouth.
Achara Catfish
Leiarius marmoratus
A massive, striking Pimelodid catfish from South America. Known for its beautiful marbled pattern and remarkably long barbels. As a strictly predatory 'monster fish', it requires a gargantuan aquarium and massive filtration. While generally peaceful towards fish too large to swallow, it will eat anything that fits into its capacious mouth. Bare-bottom or soft sand is required to prevent fatal ingestion of gravel.
Wels Catfish (European Catfish)
Silurus glanis
The Wels Catfish is a massive, highly predatory freshwater fish native to Eastern Europe and parts of Asia. As one of the largest freshwater fish in the world, it is wholly unsuited for standard home aquariums and requires a heavy-duty heated indoor pond or massive custom setup. They are highly opportunistic predators that will swallow any tank mate that fits into their enormous mouths.