Egg-laying toothcarps, commonly known as killifish, represent one of the most fascinating groups in the aquarium hobby. They differ from live-bearing toothcarps primarily in their reproductive method; since spawning and fertilization take place outside the female's body, the male does not require a gonopodium. Instead, many species exhibit extreme coloration used to attract females, often in murky water conditions.
Annual vs. Non-annual Species
One of the most unique traits of killifish is their adaptation to extreme environments. They are typically divided into two groups: *Annual species:** Inhabit temporary pools that dry up during the dry season. Their eggs can survive in a state of dormancy in moist mud (diapause) and only hatch when the rainy season returns. *Non-annual species:** Found in permanent streams and swamps. These species have longer lifespans and lay their eggs among fine-leaved plants or tree roots.
Aquarium Care and Behavior
Killifish are found worldwide in tropical and sub-tropical climates. In the aquarium, they often require dimmed lighting and plenty of hiding spots such as plants or driftwood. As many species are excellent jumpers, a tight-fitting lid is an absolute necessity. They thrive best on live or frozen foods, which stimulate their natural hunting instincts and ensure the most vibrant colors.
Breeding
Breeding killifish is a specialized niche within the hobby. For annual species, untreated peat moss is often used as a spawning substrate, which is later removed and stored moist for a period. For non-annual species, 'spawning mops' made of synthetic yarn or Java moss are ideal for collecting the eggs.
