Tench

Quick facts

Adult size

50 cm, 2500 g typical harvest weight

Days to harvest

540 to 1095 days from fingerling

Lifespan (max)

up to 20 years

Diet

omnivore

Temperature class

cool-water

Difficulty

beginner

Water parameters

Temperature range

4–28°C (optimum 22°C)

pH

6.5 to 8.5

Hardness

5 to 30 dGH

Minimum tank

500 L per individual at harvest size

Feed and growth

Feed protein

30% target

Daily feed (warm water)

1.40% of body weight per day

Daily feed (cool water)

0.60% of body weight per day

Max stocking density

40 g per litre of system water

A 2500g adult eats about 35.0 g of feed per day at optimum temperature. For a roster of 10 fish at adult size, that's around 350 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 lakes, ponds, and slow rivers across Europe and western Asia, from Britain east to Siberia and from Scandinavia south to the Mediterranean. The species (Tinca tinca) is a medium-sized cyprinid found in warm, weedy, still water with soft muddy bottoms. Adults reach 50–70 cm and 2–5 kg. Tench are benthic omnivores that root through mud for insect larvae, mollusks, and plant material. The body is stocky with small scales, an olive-green coloring, and a thick mucus coating. The flesh is white, firm, and well-flavored, though the strong mucus coat makes cleaning laborious. Tench have been cultured in European farm ponds since the medieval period and remain a traditional food fish in Central and Eastern Europe. A golden color variant is popular in ornamental ponds.

Climate and outdoor ponds

Climate classification

temperate (handles seasonal swings)

Outdoor pond zones (USDA)

4 to 10 (winter low around -34°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 cool-water to warm-water food fish for European aquaponics, with characteristics between common carp and crucian carp. Temperature range: 4–30°C, optimal at 20–26°C. Growth is moderate: 300–600 g in 18-24 months on commercial carp pellet (28-32% protein). FCR is approximately 2.0-3.0, less efficient than common carp. Tench tolerate low dissolved oxygen better than most European fish (they survive brief periods below 1 mg/L) and handle a wide pH range (6.0-9.0). Stocking density: 10-20 g/L. The species is hardy and disease-resistant, with a reputation for recovering from injuries that would kill other fish (in folk tradition, tench were called 'the doctor fish' because other fish supposedly rubbed against them for healing, likely due to the antimicrobial properties of the thick mucus). Fingerlings are available from carp hatcheries across Europe. Legal throughout Europe without special permits. Tench grow more slowly than common carp and are less commonly chosen for intensive aquaculture, but they fill a niche for traditional food production in extensive pond systems and for operators who want a native European species. The flesh quality is good enough to support local market sales, especially in Central European communities familiar with the fish.

Further reading

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