Pond Loach

Fascinating facts about the Pond Loach

• A single pond loach can stretch up to 28 cm (11 in) in standard length, yet most adults stay between 10 and 20 cm (3.9–7.9 in), with females generally outgrowing males.
• When a storm approaches, these "weather" loaches sense the falling barometric pressure and erupt into frantic swimming or stand on end, a behavior that gave them their common name.
• Unlike most fish, pond loaches can survive out of water for hours by coating themselves in a moisture-trapping mucus, switching metabolism to produce non-toxic alanine instead of ammonia, and even exhaling ammonia as harmless NH₃ gas.
• In East Asian aquaculture the species ranked 30th by total weight in 2018, but by sheer numbers it became the most farmed fish in the world, supplying dishes like Korean chueo-tang and Japanese dojō nabe.
• Introduced to Australia in the 1960s, the loach was first spotted in the wild in 1980, declared a Class 1 noxious species in New South Wales, and now populates rivers as far downstream as the Murray, illustrating how a tiny aquarium pet can become a continental invader.

At a glance

About the Pond Loach

The pond loach (Misgurnus anguillicaudatus) glides through freshwater with an eel-like silhouette, typically 10–20 cm long but capable of reaching 28 cm. Its body shimmers in shades from pale gray and olive-green to vivid pink or orange, while a trio of barbels fringe its mouth, constantly probing soft substrates for hidden invertebrates. In the slow-moving streams, rice paddies, and pond margins of its native range, from Siberia to northern Vietnam and Japan, these bottom-dwelling omnivores sift through silt, snatching insect larvae, tiny crustaceans, mollusks, and detritus. Their hardy nature lets them endure poor water quality, and when water recedes they secrete a moisture-trapping mucus layer, allowing brief terrestrial excursions. Remarkably, the loach can breathe atmospheric air and metabolically suppress ammonia production, converting potential toxins into harmless alanine and glutamine, a physiological feat that lets it survive out of water for hours. This adaptability, combined with their famed “weather” instinct, bursting into frantic swimming as barometric pressure drops, makes them both a resilient wild survivor and a charismatic aquarium inhabitant, often seen play-acting dead on smooth stones before springing back to life.

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