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

Native to rivers and lakes across Europe, from Germany east through Poland, the Danube basin, the Balkans, and into the Caspian and Aral Sea basins. The species (Silurus glanis) is the largest freshwater fish in Europe, reaching 2–3 m and over 150 kg in exceptional cases (historical records claim specimens exceeding 300 kg). Found in slow-moving, deep rivers and lakes, typically near submerged structure. Wels catfish are nocturnal ambush predators that eat fish, crayfish, frogs, waterfowl, and occasionally small mammals. The species has been introduced widely within Europe and is expanding its range due to warming temperatures. In the Ebro River in Spain and the Po River in Italy, introduced populations have reached enormous sizes and attract sport fishing tourism. The flesh is white, firm, and relatively boneless in larger specimens.

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-water to temperate food fish for European aquaponics, the continental counterpart to North American catfish culture. Temperature range: 8–30°C, optimal at 24–28°C. Growth is fast in warm water: 1–3 kg in the first year, continuing to grow rapidly for several years. FCR on high-protein pellet (40-48% protein) is 1.2-1.7, excellent for such a large species. Stocking density: 15-30 g/L for juveniles, lower for larger fish. Wels catfish tolerate moderate water quality: DO above 3 mg/L, pH 6.0-8.5. They're more sensitive to low oxygen than African sharptooth catfish but hardier than trout. The species accepts pellet feed when trained as fingerlings, though some individuals prefer meaty frozen food. Cannibalism is a serious concern: wels catfish are highly predatory and larger individuals will eat smaller tankmates. Strict size-grading is mandatory. Fingerlings are available from catfish farms in Hungary, the Czech Republic, Germany, and other Central European countries. Legal throughout most of continental Europe. In Britain, wels catfish are restricted. The species is unknown in US aquaculture. For European aquaponics in warm-temperate to continental climates, wels catfish offer fast growth and a familiar food product.

Further reading

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