Koi Guppy

Looks how to spot one

Scales and fins

Koi guppies have a slender, streamlined body with a large, flowing tail fin and a high dorsal fin. The body is covered in small, overlapping scales. The koi variety is distinguished by a clean white base colour broken by bold, sharp blocks of red on the head, shoulders or tail, mimicking the pattern of Japanese koi carp. Males are smaller and far more colourful than the plain silver-grey females.13

Personality what they are like

Koi guppies are peaceful, active fish that do well in calm community tanks. Males may chase each other occasionally but serious aggression is rare. They should not be kept with fin-nipping species or large predators that might eat them.142

Daily activity how busy a day looks

They are active swimmers that appreciate open water for swimming as well as planted areas for resting. Strong currents should be avoided.4

Grooming and care the hands-on bits

Easy to care for. A stable, cycled aquarium with regular partial water changes is essential. The tank should have a gentle filter and a lid, as guppies can jump. Floating plants help diffuse light and provide cover for fry.42

Home where they are happiest

Minimum tank size 38 litres (10 gallons). Water temperature 17-28°C (63-82°F), pH 7.0-8.5, hardness 9-19 dH. They prefer moderately hard, alkaline water and cannot tolerate temperatures below 15°C. A planted tank with floating vegetation is ideal.45

Food basics what goes in the bowl

Omnivorous. A varied diet is crucial for maintaining the red colouration. Feed high-quality flake or pellet food, and supplement with colour-enhancing foods containing astaxanthin and spirulina 2-3 times per week. Live or frozen brine shrimp, daphnia and bloodworms are excellent treats.14

Company who they like around

Peaceful community fish best kept in groups with other calm species such as small tetras, rasboras, corydoras and other livebearers. Avoid fin-nippers like tiger barbs or serpae tetras. Males can be kept together but may show mild rivalry; a ratio of two or three females per male reduces stress.41

The story where it all began

The koi guppy is not a wild species but a selectively bred colour strain of the common guppy (Poecilia reticulata). It was developed by breeders to imitate the bold red-and-white patchwork pattern of Japanese koi carp. Unlike the plain silver-grey wild type, the koi strain has a clean white body with sharp blocks of crimson on the head, shoulders or tail. The red colour comes from carotenoid pigments that the fish must obtain from its diet. Selective breeding for this pattern has shortened the lifespan compared to wild guppies, from up to 5 years down to 2-3 years.13