Wels catfish

Water parameters

Minimum tank: 5000 L per individual at harvest size.

Feed and growth

Feed protein

40% target

Daily feed (warm)

1.20% of body weight

Daily feed (cool)

0.50% of body weight

Max density

45 g per litre

A 60000 g adult eats about 720.0 g of feed per day at optimum. 10 fish at adult size: ~7200 g daily.

Legality

Rules vary by jurisdiction and change over time. Verify with your local fisheries or wildlife authority before stocking.

Unlisted jurisdictions default to "check local regulations".

Origin and habitat

The largest freshwater fish native to Europe, found across central, southern and eastern parts of the continent in the basins of the Baltic, Black and Caspian seas, in slow, deep rivers and lakes near submerged cover. Solid records put the maximum at about 2.7 m and 130 kg, while older claims of 5 m and over 300 kg are doubtful, tangled up with misidentification and unit errors; the fish can live around 20 to 30 years and exceptionally to about 60. Wels are nocturnal ambush predators, taking fish, crayfish, frogs, worms, tadpoles, the odd waterbird or small mammal, and carrion, with juveniles eating invertebrates. Stocked widely as a sport fish, its range now runs from the British Isles to western China, and introduced giants in the Ebro in Spain and the Po in Italy draw angling tourism. The flesh is white, firm and nearly boneless in big fish.

Climate and outdoor ponds

Climate

temperate (handles seasonal swings)

USDA zones

3–11 (winter low around -40°C or warmer)

Heating needed

no

Cooling needed

no

Care notes

A warm-temperate food fish for European aquaponics, the continental equivalent of North American catfish culture. It has been raised in central and eastern European carp ponds for over a century, with a smaller intensive sector in heated or geothermal water; fingerlings are often started near 26°C and grown in recirculating systems at 24–26°C on commercial pellet. Its growth capacity is among the highest of any fish, putting on roughly 1–3 kg in the first year in warm water, and feed conversion is favourable, on the order of 1.2 to 1.8. Total European farmed output is modest, around 2,000 tonnes across about ten countries, with Hungary's industry dating to the 1920s. It tolerates moderate water, with dissolved oxygen above about 3 mg/L and a wide pH band, though it is less hypoxia-tough than African sharptooth catfish. Cannibalism is real but lower than in African catfish, so size grading still matters. The fish takes pellets when trained young, though some prefer meaty or frozen food. Fingerlings come from catfish farms in Hungary, the Czech Republic, Germany and elsewhere in central Europe. It is legal across most of continental Europe, restricted in Britain, and absent from US aquaculture, where large non-native catfish are widely banned.

Further reading

• Aquaponics water chemistry: balancing pH for fish and plants
• Fish for aquaponics: tilapia vs everything else