Koi Betta Care Guide - Aquarium Setup, Feeding & Breeding

Koi Bettas are ornamental Betta splendens named for their marbled red, orange, yellow, black and white patterning, which recalls the colouration of koi carp. Their markings can change as they mature, and individual fish may develop striking patches, speckles or contrasting areas across the body and fins. The variety occurs in several tail forms, including plakat, halfmoon and crowntail types.

Like other bettas, Koi Bettas are intelligent, observant fish with bold personalities. They often investigate activity outside the aquarium, flare their gill covers during displays and may learn to recognise their keeper. Males are especially territorial, although temperament varies considerably between individuals.

Betta splendens is a labyrinth fish, meaning it can breathe atmospheric air using a specialised labyrinth organ. This adaptation allows the species to survive in warm, shallow waters that may be poorly oxygenated, including rice fields, marshes, ponds and sluggish streams.

The domestic betta has a long history in Southeast Asia, where wild fish were collected and selectively bred for fighting and later for colour, finnage and form. Modern Koi Bettas are prized for their highly variable patterns, with no two fish necessarily looking alike.

Koi Betta is a selectively bred colour variety of Betta splendens rather than a separate wild species. Betta splendens originates in mainland Southeast Asia, especially Thailand, Cambodia, Laos and Vietnam, where wild populations inhabit shallow, slow-moving freshwater environments.

A single Koi Betta should have at least 20 litres, with 30 litres or more preferable; a tank around 45 cm long provides useful swimming area and makes stable water conditions easier to maintain. Use a secure lid because bettas can jump, gentle filtration with low flow, and a heater. Provide broad-leaved plants, floating cover, shaded areas and smooth furnishings, while leaving open water near the surface for easy access to air. A fine, smooth substrate such as sand or rounded gravel is suitable, and sharp décor should be avoided because it can damage the flowing fins of long-finned forms.

Up to about 7 cm (2.8 in) in total body length, excluding exceptionally extended fin rays. Males often appear larger because of their more developed fins, while females usually have shorter fins and a slightly deeper-bodied profile.

Koi Bettas are carnivorous insectivores. Offer a varied diet based on high-quality betta or carnivorous micro-pellets, supplemented with frozen or live foods such as bloodworms, brine shrimp, daphnia and mosquito larvae. Small portions fed regularly are preferable to overfeeding, and uneaten food should not be allowed to accumulate.

A Koi Betta may live with peaceful, non-territorial tankmates such as small rasboras, ember tetras, harlequin rasboras, kuhli loaches, small Corydoras and calm snails or shrimp, provided the aquarium is spacious and carefully monitored. Avoid fin-nipping species, boisterous fish and other labyrinth fish that may compete for territory. Male Koi Bettas should not be housed with other males, and females can also be aggressive; mixed-sex groups are best avoided except during controlled breeding.

Koi Bettas breed by bubble nesting. Condition a male and female separately with nutritious foods, then place them together in a carefully prepared breeding tank with calm, warm, shallow water and floating cover. The male embraces the female beneath the nest as eggs are released, collects them and places them in the bubbles. Remove the female after spawning, and separate the male once the fry are free-swimming. The tiny fry initially need infusoria or another suitably small first food before progressing to larger foods.

Males generally have longer, fuller fins and stronger colour development, particularly in long-finned varieties. Females usually have shorter fins, a rounder abdomen and may show a small white ovipositor spot between the pelvic and anal fins; body size differences are modest and can be difficult to judge in young fish.