Killifish are a diverse group of small, colorful freshwater fish belonging to the order Cyprinodontiformes. They are categorized based on their habitat, breeding behavior, and lifespan. Here are the main categories of killifish:
1. By Lifespan
Killifish are often grouped by how long they live and their preferred environment:
- Annual Killifish
- Found in temporary pools and seasonal wetlands (e.g., African and South American species).
- Complete their life cycle in less than a year (hatch, grow, breed, and die as their habitat dries up).
- Examples:
- Nothobranchius spp. (Africa)
- Austrolebias spp. (South America)
- Pterolebias spp. (South America)
- Semi-Annual Killifish
- Live in habitats that may dry up occasionally but not every year.
- Can live 1–2 years in captivity.
- Examples:
- Simpsonichthys spp. (South America)
- Cynolebias spp. (South America)
- Non-Annual Killifish
- Found in permanent waters (streams, rivers, swamps).
- Live 2–5 years in captivity.
- Examples:
- Aphyosemion spp. (Africa)
- Fundulopanchax spp. (Africa)
- Rivulus spp. (Central/South America)
2. By Breeding Behavior
Killifish have unique reproductive strategies:
- Bottom-Spawners
- Lay eggs in substrate (mud, peat moss, or fine gravel).
- Common in annual killifish (e.g., Nothobranchius, Austrolebias).
- Plant-Spawners (Adhesive Eggs)
- Attach eggs to plants or roots.
- Examples:
- Aphyosemion spp.
- Fundulopanchax spp.
- Peat-Spawners
- Lay eggs in peat moss, which can be dried and rehydrated to trigger hatching (common in annuals).
- Mop-Spawners (Artificial Breeding)
- Breeders use synthetic yarn “mops” to collect eggs easily.
3. By Geographic Origin
- African Killifish
- Mostly from temporary pools (e.g., Nothobranchius, Aphyosemion).
- South American Killifish
- Includes annuals (Austrolebias, Cynolebias) and non-annuals (Rivulus).
- Central American & North American Killifish
- Fundulus spp. (e.g., Banded Killifish).
- Asian & European Killifish
- Rare, but some Aphanius spp. (e.g., Mediterranean killifish).
4. Popular Genera in the Aquarium Trade
| Genus | Type | Region | Notable Species |
|---|---|---|---|
| Nothobranchius | Annual | Africa | N. rachovii (Bluefin) |
| Aphyosemion | Non-annual | Africa | A. australe (Lyretail) |
| Fundulopanchax | Non-annual | Africa | F. gardneri (Steel Blue) |
| Austrolebias | Annual | South America | A. nigripinnis (Blackfin Pearlfish) |
| Rivulus | Non-annual | South America | R. cylindraceus (Cuban Killifish) |
| Epiplatys | Non-annual | Africa | E. dageti (Clown Killifish) |
5. Specialized Care Requirements
Can live several years.
Annual Killifish
Need peat incubation for eggs.
Short lifespan (6–12 months).
Non-Annual Killifish
Prefer stable water conditions.