Amur Sleeper (Perccottus glenii)

Extremely — the cockroach of the sleeper family. Astonishing tolerance: 15–30 °C, air-breathing through low oxygen, forgiving water, unfussy diet. The real caveat is its 'sleeper' nature — it's a nocturnal ambush fish, nearly motionless by day, with the display being nighttime hunting behavior and its odd morphology. Keepers wanting daytime activity will be disappointed; those who enjoy watching patience will be fascinated.

Two sources: 'Amur' (the Amur River = Heilongjiang) is its native range — the Russian Far East, northeast China, and the Korean Peninsula. 'Sleeper' is the English name for Odontobutidae, from their daytime stillness, appearing asleep. The Japanese 'Manshū-donko' (Manchurian mudfish) likewise pairs origin with habit. It also carries a famous identity: the 'ecological bomb' invading Europe, listed as a priority invasive species in the EU.

Short oxygen crashes won't kill it; long-term filtration still matters. It's the low-oxygen champion of its family, gulping air directly — a survival necessity in native still waters (swamps, rice paddies). Keep filtration running anyway: low oxygen won't kill it, ammonia will. Keep flow gentle; it's a still-water ambusher.

Carnivore, moderately unfussy: small fish, shrimp, aquatic insects, earthworms. Prepared-food acceptance is middling — live and frozen lead, with pellet training requiring patience (fast, then tease with live food, then switch to frozen). Its hunting style is wait-and-burst: food crossing the strike zone triggers an instantaneous attack. Dangle food with tweezers to watch textbook ambush predation.

Not recommended. It's an ambush hunter; anything swallowable is 'sleeping prey' — including same-size fish you assumed were 'companions'. The sleeper's terror is that it stays still by day so you assume safety; by night it moves, and the tank is one fish short. Solitary is the only scheme that guarantees everyone else's safety.

Yes, and its leaps are catapult-grade — ambush fish all pack extreme burst power. Lid mandatory, every cord opening sealed. Jumping drive peaks during the first weeks of acclimation. Its amphibious endurance resembles snakeheads (air-breathing), so an escapee survives damp floors a long time — search immediately rather than waiting for it to dry out.

That's the core habit, not illness. Odontobutids run an extreme energy strategy: zero-consumption stillness in caves or sand by day, active hunting at night. Keepers must embrace 'passive viewing' — the joy is nocturnal behavior. For daytime activity, choose characins or cyprinids, not sleepers.

It's native to Heilongjiang basin still waters (swamps, paddies, slow channels) at the Russia-China-Korea junction. Introduced to Central Asia and Europe in the 20th century, it became a nightmare through astonishing tolerance and fecundity — surviving anoxic, cold, polluted water while eating local eggs and fry, and landing on EU invasive-species control lists. A reminder that its 'ease' is a double-edged sword: never release it under any circumstances.

Home successes exist. It's a bottom spawner; breeding males turn territorial, females deposit eggs in crevices or caves, and males guard. Hatching takes about a week; fry start on baby brine shrimp. Post-maturity aggression means pairing needs 300 L+ water, or grow a small group up and let pairs form naturally.

Five to eight years, ten with fine care. The longevity-plus-low-maintenance combination is rare among natives — many keepers' sleepers are the tank's 'easiest fish', quietly accompanying them for years with good feeding and stable water. It's not an 'interactive' pet fish; it's an 'observational' long-term roommate.