Crucian carp

Carassius carassius

Also known as Crucian, European crucian carp

FreshwaterFish

Crucian carp (Carassius carassius) — Viridiflavus · CC BY-SA 3.0

Care at a glance

Temperature: 39–75°F (4–24°C)
pH: 6.5–8.0
Adult size: 11.8 in (30 cm)
Minimum tank: 119 gal (450 L)
Temperament: Peaceful
Social behavior: Social
Swim level: Bottom
Difficulty: Easy
Breeding: Medium
Rarity: Common
Origin: Native to ponds, lakes, and slow rivers across Europe and western Asia.
Family: Cyprinidae

Overview

Crucian carp are pond fish that need a group and a lot of space, so plan on a pond or a very large tank of at least 450 litres with strong filtration. They are a temperate species that does best in cool water from about 4 to 24 C and needs no heating in most climates. Feed a varied omnivore diet of sinking pellets, plant matter, and frozen or live foods such as bloodworm. They are peaceful and mix well with goldfish and other cool-water pond fish.

In the wild

The crucian carp is a hardy, deep-bodied pond fish from still and slow waters across Europe and western Asia. It lives among thick plants in ponds, lakes, and backwaters, rooting through soft substrate for food. It is famous for surviving very low oxygen and cold that would kill most fish, including long spells under winter ice. This is a temperate pond fish rather than a tropical aquarium species.

Good to know

Carassius carassius can survive months of near-zero oxygen by switching to an unusual metabolism that turns waste lactic acid into alcohol, which it releases through the gills. It is a close relative of the goldfish, Carassius auratus, and the two can hybridise. It commonly reaches 15 to 25 cm and can grow larger in a big pond.

Did you know

It is one of the toughest of all freshwater fish, able to spend a whole winter sealed under ice in oxygen-starved water by producing alcohol instead of suffocating.