Paradise fish

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

Omnivore. Takes the usual range of dry and frozen foods (flake, pellets, frozen bloodworm and brine shrimp) and will also hunt live insects and worms at the surface. Some greens, such as a small piece of blanched vegetable, is a useful addition. Feed once or twice a day; live food helps with color and triggers spawning behavior.

Compatibility

• Sometimes described as a community gourami, which is misleading. Males are territorial, aggressive with each other, and tend to push smaller or slower tankmates around. Treat it as semi-aggressive when planning a stocking list
• A single male with two or three females usually works in a roomy planted tank, ~100 L or larger. Outside of breeding, mixing with sturdier, faster tankmates such as larger tetras, barbs, danios, and bottom catfish is more reliable than pairing with delicate or long-finned species
• One of the few showy tropical-looking fish that does not need a heater. Comfortable at typical indoor room temperatures and tolerated by outdoor ponds during warm months
• An early member of the European ornamental hobby (imported 1869), well before tropical fishkeeping became widespread

Origin and habitat

An anabantoid native to East Asia, ranging through southern China from the Yangtze drainage down to Hainan Island, plus Taiwan and northern Vietnam, with feral populations now established in warm and warm-temperate regions worldwide. As a labyrinth fish it can gulp air at the surface and gets along in oxygen-poor water that would suffocate most fish: rice paddies, ditches, swamps, slow creeks, and stagnant ponds. Its other unusual trait, given its bright coloring, is cold tolerance, and it stays healthy at room temperature without a heater. Adult males grow to roughly 10 cm total length with long fins and bold red-and-blue or red-and-green vertical barring; females are smaller, around 7 cm, with shorter fins and duller color. Males are also notoriously scrappy with one another. Spawning happens at a male-built bubble nest at the surface, with the male tending the eggs and fry. The species has a long captive history, having been brought to Paris in 1869, which makes it one of the oldest ornamental fish in the European hobby (the goldfish predates it). Several captive lines exist, including albino, xanthic, red, blue, and stripeless forms.

Breeding

Spawns at a bubble nest the male constructs at the surface, usually anchored to floating plants. Once the nest is ready the male shows off with flared fins and saturated color to attract a female, and the pair spawns beneath the nest in the wrap-and-release embrace typical of anabantoids. The eggs contain an oil droplet, float up into the nest on their own, and the male takes over from there, repairing the nest, catching falling eggs, and guarding the larvae for the first few days while they finish absorbing their yolk. Pull the female out once she has finished, since the male will drive her off, and remove the male once the fry are swimming freely. The newly free-swimming fry are tiny and start on infusoria-sized food before graduating to baby brine shrimp. Spawning is not difficult to set up, which helped the species catch on early in the European hobby.

Common problems

The defining problem with this fish is its temper. Males will fight other males and bully slow, small, or similar-looking tankmates, with bettas and dwarf gouramis being particularly bad pairings since the vertical bars on their flanks read as a rival. A large, heavily planted tank with broken sightlines takes the edge off but does not eliminate it. Health-wise the species is otherwise undemanding: it handles cool water well, copes with a wide range of conditions, and rarely runs into disease in a clean tank. Reported lifespans run roughly 5 to 8 years, occasionally to about 10.

Outdoor pond suitability

Climate

temperate

USDA zones

6–11 (winter low around -23°C or warmer)

Outdoor pond at least 60 cm deep for thermal mass. Local frost depth and surface freezing matter.

Bioload

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size