Paradise fish

Quick facts

Adult size

10 cm

Lifespan

can live up to 8 years

Tank zone

top

Temperament

aggressive

Difficulty

beginner

Water parameters

Temperature

15–26°C

pH

6.0 to 8.0

Hardness

5 to 20 dGH

Tank requirements

Minimum volume

75 L

Minimum length

60 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Lid

required - jumper

Feeding

Diet: carnivore, feeds primarily at the top.

Omnivore that eats anything. Flake, pellets, frozen bloodworm, frozen brine shrimp, live food (insects, worms), and blanched vegetables. They're surface and midwater feeders that also pick food from plant leaves and the substrate. Feed once or twice daily. Live food triggers breeding behavior and the best coloring.

Compatibility

• Aggressive for a gourami. Males are territorial and will fight other males, harass females, and bully slow-moving tankmates. Not a peaceful community fish despite sometimes being described as one.
• Best kept as a single male in a community with robust species: barbs, larger tetras, danios, and catfish. Avoid long-finned or slow species. A single male with 2-3 females works in a 100 L tank with dense planting.
• Cold-water species. One of the few tropical-looking fish that thrives at 15–22°C. Suitable for unheated indoor tanks and outdoor ponds during warm months.
• Historical significance: the paradise fish was one of the first tropical fish kept in aquariums, imported to France in 1869. It predates the modern tropical fish hobby by decades.

Habitat

Native to still and slow-moving water across China, Korea, Taiwan, and Vietnam. Found in rice paddies, ditches, ponds, and slow streams with dense vegetation. The species (Macropodus opercularis) was among the first 'tropical' fish imported to Europe, arriving in France in 1869. It's a labyrinth fish that breathes atmospheric air, allowing it to survive in low-oxygen, stagnant water. The body is striking: alternating vertical bars of blue and red-orange, with flowing fins in males. Males are significantly more colorful and larger-finned than females. Several color variants exist: blue, albino, and dark. Adult size is 8–10 cm for males. The species tolerates a temperature range of 10–28°C, making it one of the most cold-tolerant labyrinth fish. It's been introduced outside its native range (including parts of the United States) where escaped or released aquarium fish have established feral populations. Commercially bred but less commonly available than in previous decades, as flashier tropical species have taken over market share.

Breeding

Bubble nest builder. The male constructs a large nest of bubbles at the surface among floating plants. Courtship involves dramatic displaying: the male spreads his fins, deepens his colors, and circles the female aggressively. Spawning follows the typical anabantoid embrace beneath the nest. The female releases 50-300 eggs per embrace, and the male places them in the nest. Multiple embraces produce 500-1000 eggs in a large spawn. The male guards the nest aggressively and should be left with the eggs; remove the female. Eggs hatch in 24-48 hours. Fry become free-swimming in 3-4 days. Remove the male once fry are swimming. Fry eat infusoria for a few days, then baby brine shrimp. Growth is fast. Paradise fish are prolific and easy to breed, which contributed to their historical popularity.

Common problems

Aggression is the defining management challenge. Male paradise fish are fighters; two males in the same tank injure each other severely. Even in a community, a single male harasses slow or passive tankmates. Tank size and dense planting help but don't eliminate the behavior. Cold tolerance is an advantage that's often ignored: keepers put them in tropical setups at 26°C when they'd be healthier at 18–22°C. Health problems are rare at cool temperatures. Ich and bacterial infections appear mostly in overheated tanks. The species is tough and long-lived (5-8 years) in appropriate conditions.

Outdoor pond suitability

This species is suited to outdoor ponds, not just indoor aquariums.

Climate classification

temperate

Outdoor pond zones (USDA)

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

Outside the zone range, this species can still be kept indoors. Within the zone, an outdoor pond at least 60 cm deep usually has enough thermal mass to overwinter the species, though local frost depth and surface freezing matter.

Bioload

Bioload coefficient: 2.0 (medium-bodied labyrinth fish; similar to a small gourami).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

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