Golden wonder killifish

Quick facts

Adult size

10 cm

Lifespan

can live up to 5 years; longer-lived than most killifish; 3-5 years typical

Tank zone

top

Temperament

semi-aggressive

Difficulty

intermediate

Water parameters

Temperature

22–26°C

pH

6.0 to 8.0

Hardness

5 to 20 dGH

Tank requirements

Minimum volume

110 L

Minimum length

80 cm

Flow

low

Lighting

dim preferred

Substrate

any

Hiding spots

needed

Open swimming room

needed

Lid

required - jumper

Feeding

Diet: carnivore, feeds primarily at the top.

Surface feeder with a predatory streak. Flake, floating pellets, frozen bloodworm, frozen brine shrimp, live food (fruit flies, mosquito larvae, small crickets, live guppies for larger specimens). They hunt by lurking at the surface and ambushing anything that falls in or swims past. Live food triggers the most active feeding behavior. In community tanks, they eat floating food before it can sink to other fish. Feed once or twice daily.

Compatibility

• Surface-dwelling predator. Despite being a killifish, golden wonders are large enough (7–8 cm) to eat small fish. Anything that fits in their upturned mouth is food: neon tetras, guppies, small rasboras, and shrimp.
• Best with medium-sized tankmates that stay in the lower water zones: corydoras, medium tetras (black skirt, serpae), barbs, and loaches. The golden wonder patrols the surface and ignores fish below it that are too large to swallow.
• Males are territorial toward other males at the surface. One male per tank in smaller setups (under 100 L). In larger tanks, multiple males coexist if surface area is sufficient.
• Hardy, undemanding, and visually striking. The gold body with iridescent blue scales under certain lighting makes them an appealing surface fish for medium-sized community tanks.

Habitat

Native to fresh and brackish coastal waters across India and Sri Lanka. Found in ditches, rice paddies, slow streams, and mangrove-edge pools. The wild form (Aplocheilus lineatus) is olive to brown with metallic scales and red or gold spotting. The 'golden wonder' is a selectively bred gold variant that originated in Indian aquarium fisheries and became the dominant form in the hobby trade. Males are more colorful, slightly larger (up to 9 cm), and have more pointed dorsal and anal fins. Females are smaller (6–7 cm) and less vivid. The species is a non-annual killifish, meaning it lives multiple years and doesn't require a dry period for egg development. Adult lifespan is 3-5 years. Commercially bred in India and Southeast Asia. Inexpensive and widely available, though not always in stock at general pet stores.

Breeding

Egg depositor that attaches eggs to floating plants over a period of days. A pair produces 5-15 eggs daily among floating plant roots, java moss, or spawning mops at the surface. Eggs are relatively large and can be picked off by hand. Adults eat eggs and fry, so either collect eggs daily or provide very dense floating cover. Eggs hatch in 12-14 days at 25°C. Fry are comparatively large and can eat baby brine shrimp from day one. Growth is fast; fry reach 2–3 cm within a month. The species breeds readily in home aquariums without special conditioning. A well-planted surface in a species tank produces a steady stream of fry.

Common problems

Predation on small tankmates is the main issue new keepers encounter. The upturned mouth and surface-hunting behavior mean that neon tetras, endlers, and small rasboras disappear from the tank over time. Match with appropriately sized tankmates. Jumping is a significant risk; golden wonders launch from the water to catch insects and will exit through any gap in the lid. A tight cover is mandatory. Health problems are uncommon; the species is hardy across a wide range of conditions (pH 6.0-8.0, temperature 22–28°C, tolerates some salinity). Ich is rare except in stressed new arrivals.

Bioload

Bioload coefficient: 3.0 (mid-size predator with high protein diet; comparable to a young pearl 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