Tench
Slippery freshwater fish with olive-green skin and red eyes.
The tench is a stocky freshwater fish found across Eurasia in slow-moving lakes and rivers. It tolerates low oxygen levels and feeds on bottom-dwelling animals at night. Anglers prize it for its strength, while gardeners use ornamental varieties to maintain pond health.
- Tolerates low oxygen levels where carp cannot survive.
- Males have curved pelvic fins extending beyond the anus.
- Can produce up to 300,000 sticky green eggs in summer.
- Slippery skin led to the folklore name doctor fish.
- Maximum recorded length is 70 cm.
What it is
The tench is a stocky fish with a shape similar to carp. Its skin is olive-green, darker on the back and golden underneath. The tail fin is square, while other fins are rounded. Small scales are deeply embedded in thick skin, making the fish very slippery. It has a narrow mouth with tiny barbels at the corners. The eyes are small and red-orange. Males have larger, curved pelvic fins that extend past the anus, whereas females have a more convex belly profile.
Where it lives
This species lives throughout Eurasia, ranging from Western Europe, including Britain and Ireland, eastward to the Ob and Yenisei Rivers in Asia. It also inhabits Lake Baikal. Tench prefer still waters with clay or muddy bottoms and abundant vegetation. They are rare in clear, stony waters and absent from fast-flowing streams. The fish can survive in environments with low oxygen concentrations where even carp cannot live.
How it lives
Tench feed primarily at night on the bottom of eutrophic waters. Their diet consists mainly of animal matter such as chironomids, snails, and pea clams. They are shoaling fish often found in deep, slow-moving waters or gravel pits. When caught on a rod, individuals over one kilogram are known to be strong fighters. They help keep waterways clean by acting as bottom feeders.
Breeding and life cycle
Spawning occurs in summer, usually in shallow water among aquatic plants. The female deposits sticky green eggs, with a single event producing up to 300,000 eggs. Growth is rapid, and young fish may reach a weight of 0.11 kg within their first year. Sexual dimorphism is strong, with males developing noticeable muscles around the base of their pelvic fins.
Fish and people
Tench are edible and can substitute for carp in recipes, though they are not commonly eaten. They are popular targets for coarse anglers using float fishing or ledgering with baits like maggots and sweetcorn. An artificially bred variety called the golden tench is kept in ornamental ponds. These gold or red-spotted fish help maintain water health. Folklore claims their slime cured sick fish, earning them the name doctor fish.
Questions people ask about Tench
Why is the tench called doctor fish?
Folklore suggested that the thick slime on the tench's skin could cure sick fish that rubbed against it. This belief led to the common nickname doctor fish, although the slime primarily serves to make the fish slippery and difficult for predators to hold.
What do tench eat?
Tench are nocturnal feeders that prefer animal prey. They consume chironomids, snails, and pea clams from the bottom of eutrophic or well-vegetated waters. Anglers often catch them using baits such as maggots, sweetcorn, pellets, bread, and worms.
How large do tench grow?
The maximum size for a tench is 70 cm. Females can reach weights of around 7 kg, while males rarely exceed 3 kg. A record fish caught in England weighed nearly 7 kg. Most specimens encountered are significantly smaller than these maximums.
Are tench good for garden ponds?
Yes, particularly the golden tench variety. They are popular ornamental fish that act as bottom feeders, helping to keep pond waterways clean and healthy. Their colours range from pale gold to dark red, and some have black or red spots.
Good reading and sources
The facts on this page come from the Wikipedia article "Tench", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
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