European eel

Quick facts

Adult size

100 cm, 3000 g typical harvest weight

Days to harvest

730 to 1460 days from fingerling

Lifespan (max)

up to 25 years

Diet

carnivore

Temperature class

cool-water

Difficulty

advanced

Water parameters

Temperature range

8–25°C (optimum 22°C)

pH

6.5 to 8.5

Hardness

3 to 25 dGH

Minimum tank

2000 L per individual at harvest size

Feed and growth

Feed protein

45% target

Daily feed (warm water)

1.50% of body weight per day

Daily feed (cool water)

0.50% of body weight per day

Max stocking density

80 g per litre of system water

A 3000g adult eats about 45.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 450 g of feed daily.

Legality

Aquaculture and possession rules vary by jurisdiction and change over time. This table reflects regulations as of the verified date on each row. Verify with your local fisheries or wildlife authority before stocking.

Jurisdictions not listed here default to "check local regulations". A non-listing is not a green light; rules in your specific county or municipality may apply.

Habitat and origin

Native to freshwater rivers, lakes, and coastal waters across Europe, from Scandinavia to the Mediterranean, and extending into North Africa. The species (Anguilla anguilla) has one of the most remarkable life cycles in the animal kingdom: adults migrate from European freshwater to the Sargasso Sea in the western Atlantic to spawn, and the larvae drift back on ocean currents over 1-3 years, arriving on European shores as transparent 'glass eels' that migrate upstream into rivers and lakes. Wild populations have declined by over 90% since the 1980s due to overfishing, habitat loss, pollution, and parasite infection. The species is listed as Critically Endangered by the IUCN. European eel aquaculture is significant (over 6,000 tonnes annually, primarily in the Netherlands, Denmark, Italy, and Spain) but relies entirely on wild-caught glass eels because the species has never been bred in captivity at commercial scale.

Climate and outdoor ponds

Climate classification

temperate (handles seasonal swings)

Outdoor pond zones (USDA)

6 to 11 (winter low around -23°C or warmer)

Heating in a temperate climate

Not required (handles seasonal cool periods)

Cooling in a temperate climate

Not required

Zone bounds reflect year-round outdoor pond viability with no active heating. Anywhere outside the bounded zone, the species can still be kept in an indoor heated tank or a seasonally-managed system. Verify your specific microclimate, as a sheltered yard zone can run a half-zone warmer than the regional rating.

Care notes

A high-value aquaculture species with serious sustainability and ethical considerations. European eel is a premium product commanding $15-40/kg depending on market and preparation. The eel is grown in recirculating aquaculture systems (RAS) at 22–28°C from glass eels (wild-caught juvenile stage) to market size (150–300 g) in 12-24 months. FCR is 1.5-2.0 on high-protein eel pellet (45-50% protein). Stocking density in RAS: 40-80 g/L. The critical issue is that every glass eel used in culture is taken from wild populations that are Critically Endangered. EU regulations restrict glass eel harvest and require that a portion of catch be used for restocking programs. Many conservation organizations argue that eel farming increases pressure on wild stocks rather than relieving it. For aquaponics, European eel is theoretically compatible (they produce waste that feeds plants efficiently) but the ethical and regulatory complexity makes it inappropriate for most operators. Glass eel supply is limited, expensive ($500-1500/kg of glass eels), and subject to international trade restrictions (CITES Appendix II). Not recommended for home aquaponics due to conservation concerns.

Further reading

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