What Makes Killifish Special
Killifish are small egg-laying fish found across Africa, South America, and parts of Asia and the US. They range from 1-inch annuals that complete their life cycle in a single rainy season to 5-inch non-annuals that live for years. Over 1200 species are scientifically described, far more than any other aquarium fish family.
Two distinct breeding categories exist: annual killifish (Nothobranchius, Austrolebias, some Simpsonichthys) that evolved in seasonal pools that dry up annually, producing drought-resistant eggs that survive months in damp peat; and non-annual killifish (Aphyosemion, Fundulopanchax, Rivulus, American Fundulus) that live in permanent streams and produce regular continuously-developing eggs.
The killifish hobby is a global community. The American Killifish Association, British Killifish Association, and similar groups worldwide trade eggs through international mail — the drought-resistant eggs of annuals can survive weeks in envelopes, letting hobbyists share species that would otherwise never enter their region.
Annual Killifish — The Extreme Life Cycle
Annual killifish in the wild hatch at the start of the rainy season, grow explosively fast (sexual maturity in 4-6 weeks!), spawn continuously, then die as their pools dry up. Their eggs remain in damp substrate, waiting for next years rains to trigger hatching.
In captivity, breeders replicate this cycle. Setup: small bare-bottom tank (2-5 gallons) with a container of peat moss. Pair or trio feeds heavy for 2 weeks, then moves to spawning tank. Fish bury eggs in the peat during spawning, diving into the substrate to deposit each egg individually.
After 2-3 weeks of active spawning, collect the peat. Squeeze out excess water until peat is just damp. Store in a labeled zip-lock bag in a dark warm place (72-78°F). Incubation period varies by species: 2 weeks to 6 months. Shorter-season species hatch fast; longer-season species require extended diapause.
Hatching: immerse peat in soft water (RO or rainwater). Eggs detect the water cue and begin final development. Fry emerge within hours to days. Feed vinegar eels or baby brine shrimp immediately — fry grow visibly within days.
Popular annual species: Nothobranchius rachovii (red/blue African annual), Nothobranchius guentheri (vivid yellow/red), Austrolebias bellottii (South American), Simpsonichthys magnificus (Brazilian).
- ✦Collect peat after 2-3 weeks of active spawning
- ✦Squeeze to damp (not wet), store in labeled bag
- ✦Incubate 2 weeks to 6 months depending on species
- ✦Hatch by immersion in soft water
Non-Annual Killifish
Non-annual killifish live in permanent streams and lay eggs continuously like most aquarium fish. Popular species: Fundulopanchax gardneri (African blue gularis), Aphyosemion australe (orange tail), Aphyosemion striatum, Rivulus xiphidius.
Breeding setup: small tank (5-10 gallons) with yarn spawning mops (bundles of acrylic yarn attached to corks that float or sink). Fish deposit eggs on the yarn fibers. Daily, pick eggs from the mops and transfer to a separate hatching container.
Incubation: 14-28 days in water with a drop of methylene blue to prevent fungus. Watch eggs daily; remove white (fungused) eggs to protect neighbors. Fry hatch over several days — dont expect a synchronized hatching.
Growth: non-annual killifish grow more slowly than annuals. Sexual maturity at 4-8 months. Adults live 2-5 years. First food: baby brine shrimp or microworms, transitioning to small flake and frozen foods.
Non-annuals are less dramatic than annuals but easier to maintain — no egg storage, no diapause management, no sudden population crashes. Good starting point for beginning killifish breeders.
Water Conditions for Killifish
Most killifish prefer soft acidic water — pH 6.0-7.0, GH 3-8, KH 1-4. Some species require specific parameters: Aphyosemion species thrive in ultra-soft water, while Fundulopanchax species handle slightly harder conditions.
Temperature: wide range. African species generally 72-78°F. South American annuals often 74-80°F. Cooler than many tropical fish — which is why they do not thrive in community tanks kept at 82°F for tetras and discus.
Tannins are beneficial — Indian almond leaves, peat filtration, or driftwood help recreate native conditions. Many killifish species show more vivid colors in tannin-stained water.
Avoid hard alkaline water. Killifish kept in tap water from areas with high KH (most city water) often fail to breed and develop health problems. If your tap is hard, use RO water or rainwater mixed with tap to achieve soft acidic parameters.
The Killifish Egg Trading Network
One of the unique joys of killifish keeping is global egg trading. Because annual killifish eggs survive drought in damp peat, they can be mailed in envelopes worldwide. A single envelope with a pouch of peat can contain 50-500 eggs, which hatch when immersed in water.
Associations like the American Killifish Association (AKA), British Killifish Association (BKA), and the French-speaking Killifish Collective (Killi-Data) run egg exchanges where members trade rare species across continents. Joining an association typically costs $30-50 annually and provides access to species never sold commercially.
Shipping process: squeeze peat damp (not wet), seal in a plastic bag with air, pad in a padded envelope, include a species label with collection date. Domestic shipping takes 2-5 days; international 1-4 weeks. Eggs of most species survive both easily.
This system has preserved killifish species that are extinct in the wild. Some Nothobranchius species from specific African pools exist only as eggs in hobbyist collections worldwide — a remarkable example of hobby-driven conservation.