Karpfen

Only conditionally suitable as an aquarium fish; pond fish!

Coldwater ornamental fish such as koi: the tank or pond must be at least 10 times as long and 3 times as deep as the largest adult total length the species can reach.

Species over 40 cm adult size need a tank with at least 4 m² of floor area for two animals, plus 1 m² for each further animal.

Austria, general duties for freshwater fish: aim for middle values of the temperature, hardness and pH ranges; adjust new fish slowly to the water; change part of the water regularly, with water of the same quality; check temperature daily, and pH, hardness and nitrate at least every 14 days; check nitrite daily during the first six weeks of a new tank; give a clear day–night cycle; provide free swimming space, filter, heater and pump, substrate, hiding places and plants where the fish allow; keep the species according to its social structure; species kept together must suit each other in water quality, temperature and social behaviour (§ 7 (5); Anlage 5, 1.1).

Switzerland, general duties for ornamental fish: minimum volume = each fish's current body length (snout to tail base) × litres per cm by size class (up to 5 cm 0.5; 10 cm 0.75; 15 cm 1; 20 cm 1.25; 30 cm 1.75; 40 cm 2.25; over 40 cm 3), summed over all fish, plus species-specific needs; the tank at least 3 times as long and 2 times as wide as the largest fish's body length, and the water at least that deep; not visible from all sides, with visual cover and retreats; a day–night rhythm; water quality suited to the species; no prolonged strong vibration; social species need contact with their own kind; prevent excessive breeding; genetically modified fish such as GloFish are banned (TSchV Art. 13, 25, 98 and Anhang 2 Tabelle 8).