Wels Catfish

Silurus glanis is the apex freshwater predator of Europe, distributed from the Rhine and Danube eastward through Russia and Central Asia. It is the continent's heaviest freshwater fish, with verified specimens exceeding 2.5 metres and 130 kg in the wild. It inhabits deep, slow-moving sections of large rivers and lakes, lying motionless on the bottom during daylight and hunting fish, frogs, waterfowl, and small mammals after dark. Its six long barbels — two maxillary and four mandibular — are exquisitely sensitive chemoreceptors.

In the aquarium, the Wels is strictly a public-institution fish as an adult; only very large indoor pond systems can house mature specimens. Juveniles, however, are periodically available and grow at a moderate pace, making them temporarily manageable. Water temperatures from 10–25°C are tolerated, allowing unheated European fish rooms to house them. Filtration must be industrial in scale relative to the fish's size.

The Wels is an iconic species in European freshwater angling and increasingly in conservation — its role as an apex predator regulates fish community structure in river ecosystems. In the aquarium it is intelligent, learns to recognise its keeper, and can live for several decades, making any commitment to keeping it a multi-decade undertaking.

Water: 10–25°C, pH 6.5–8.0, tolerant of a wide range; cool water acceptable; high O₂. Tank: 10 000 L minimum for adults; indoor pond preferred; exceptional filtration. Feeding: Whole fish, large prawns, earthworms; very large adults can take waterfowl in the wild — feed proportionally. Breeding: Spring spawning in nest of vegetation; male guards eggs; not feasible in home aquaria. Compatibility: Will consume any fish or animal that fits in its enormous mouth — keep alone.