Family: Anguillidae
Japanese eel — a Anguillidae from E China to Japan, peaceful; keep with similar-sized calm tankmates. Reaches 52.5–77 cm; keep in a group of 4–6 for natural behaviour. 20–26 °C.
A Anguillidae species native to China and Japan: Anguilla japonica lives middle of the water column over warm freshwater streams and lakes. Peaceful; keep with similar-sized calm tankmates. Adults reach 52.5–77 cm. It is one of the aquarium-kept Anguilla species we profile, alongside Anguilla marmorata.
Yes, and success is deeply rewarding. Adults reach 52–77 cm, needing 500 L or more and strong filtration. It's a nocturnal ambush predator — the appeal is its dragon-like form patrolling the tank. Confirm you have the space and patience first.
Nocturnality is its nature. Hiding by day and patrolling at dusk is a rhythm captive life won't change. To observe it, provide large driftwood caves, feed at dusk, and watch under dim red light.
Omnivorous leaning carnivorous: juveniles take aquatic insects and small crustaceans, adults take small fish, shrimp and earthworms. In captivity feed sinking carnivore pellets, frozen bloodworms, whole small fish and shrimp meat. Vision is poor and hunting is by smell — food landing near its cave works best.
500 L is the floor; a 150 cm or longer tank is recommended. Eels are muscular and roam widely — small tanks cause bruising and stress. Run filtration at 3–5 tank volumes; they're heavy-waste carnivores.
Strong exploratory and migratory instincts drive them along glass and heater cables at night seeking a way out. The lid must fully cover the tank and gaps should be foam-sealed. An escaped eel survives hours on a damp floor — return it promptly and it usually lives.
Anguilla has a continuous dorsal fin, pointed tail and minute scales, and is catadromous (grows in freshwater, breeds at sea); Monopterus lacks fin rays, has a conical tail and no scales, and is a native burrowing fish. The true eel is slimmer and more elegant; the swamp eel is stockier and fiercer.
20–26 °C, pH 6.5–7.5, GH 5–15. They're ammonia-sensitive, and their carnivorous heavy-waste lifestyle demands weekly third water changes with efficient filtration. Keep oxygen high — their nocturnal metabolism makes oxygen shortage a common killer.
Similarly sized, gentle bottom and mid-water fish: large corydoras, peaceful catfish, larger bitterlings. Avoid small fish (they become food) and nippy species (they'll chew its fins). Eels are mildly territorial and rarely initiate attacks.
Juveniles grow quickly — 15–20 cm in a year; growth slows with age. They reach maturity in captivity, but the catadromous breeding migration can't happen in a tank — a home eel will never breed, a biological fate no aquarist can change.
Wild eels reach 15–20 years; in home aquaria 8–12. They're a living-fossil class of fish — keeping an eel is keeping a piece of river ecology history at home.