KILLIFISH

KILLIFISH

Killifish are widespread across Africa, Asia, South America, North America, and parts of Europe. These fish inhabit almost every type of freshwater biotope. More than 500 species are recognized in this group, with several species also found in brackish water, and a few even living in pure salt water. Killifish are well known for their adaptability, with some species thriving in temporary bodies of water that dry up during the dry season. Others, such as the Desert Pupfish (Cyprinodon species), have been found in water temperatures as high as 116.6°F (47°C). This is remarkable, considering that this temperature is well above the lethal threshold for most vertebrates. Due to their wide distribution, killifish have developed unique adaptations, including a fascinating reproductive cycle that allows them to survive extreme environmental changes.

Killifish included in this work:

SIZE: Most killifish are small, ranging from 2 to 3.5" (9 cm), with only a few species exceeding 8" (20 cm).

TANK: For most species, a tank measuring 24" (41 cm) with a capacity of 10-20 gallons (38-76 L) is sufficient for a pair. Although killifish inhabit various environments, most prefer shallow tanks with little or no water circulation. The tank should be well planted, with floating plants providing some shade. Dark gravel and hiding places, such as driftwood, roots, and rocks, should be included. A tight-fitting cover is essential, as many species are excellent jumpers.

WATER: Water parameters vary depending on the species' natural habitat. Most Aphyosemion species thrive in water with a pH of 5.5-7.0, a hardness of 3-10 dH, and a moderate temperature. Aplocheilus species prefer a pH of 6.0-7.5 and a hardness of 3-10 dH. Species from genera such as Cynolebias, Epiplatys, Nothobranchus, Pachypanchax, Pseudepiplatys, Pterolebias, and Rivulus require a pH of 6.0-7.0 and a hardness of 4-12 dH. Lamprichthys species need more alkaline water, with a pH of 7.5-8.5 and a hardness of 10-20 dH. Many species are often kept in water that is too warm, so it is essential to refer to specific species descriptions for ideal conditions.

SB: Despite their small size, many male killifish are aggressive towards one another. It is often best to keep only one pair per tank to prevent conflicts. In larger tanks, multiple pairs can be housed together, provided there are plenty of hiding places. Killifish are generally good community fish when kept with small, peaceful species that thrive in similar water conditions.

SC: Most killifish are compatible with other small, peaceful species. Aphyosemion species from West Africa can be housed with South American tetras, hatchetfish, pencilfish, Corydoras, Loricariids, and select Asian species such as Trichopsis, Pangio, and Puntius titteya. Compatibility depends on the specific species of killifish, so it is best to consult individual descriptions.

FOOD: Surface-dwelling killifish, especially those with an upturned mouth, primarily feed on small flying insects. Other species consume insect larvae, aquatic insects, and crustaceans. Bottom-dwelling killifish feed on river worms, insect larvae, and crustaceans. In aquariums, they readily accept live foods and, once acclimated, will also consume flake foods.

SEX: Males are generally more colorful than females and are easily distinguished by their brighter patterns and fin shapes.

B: Killifish have developed unique spawning behaviors as an adaptation to their environments. They are classified into two main reproductive types: "annual" and "non-annual" species. These groups further divide into bottom spawners and substrate spawners.

'ANNUAL' KILLIFISH
Most annual species require a small breeding tank of about 5.5 gallons (21 L). A substrate of fine sand or peat moss is recommended. An alternative method is using a container with a lid and a small hole, filled with peat moss for spawning. Once spawning occurs, the peat moss is removed and stored in a plastic bag or container at 77°F (25°C) for a period of one to four months. After the storage period, the peat is reintroduced into the tank, triggering the fry to hatch. Fry should be fed Drosophila, newly hatched brine shrimp (Artemia), and infusoria.

In the wild, annual killifish live in temporary bodies of water that dry up seasonally. They have a short lifespan, laying their eggs in mud before perishing. The eggs survive dry periods and hatch with the return of rains. Some species undergo diapause, a developmental pause that allows embryos to hatch at different times, increasing survival chances.

"Burying" semi-annual killifish, such as some Aphyosemion, Epiplatys, and Procatopus species, lay their eggs near the water's edge. These eggs can survive exposure to air and hatch when submerged again, often triggered by low oxygen levels.

'NON-ANNUAL' KILLIFISH
Non-annual species typically spawn in well-planted tanks, although adults may eat their own eggs. A spawning mop or fine-leaved plants can serve as egg-laying sites. Once laid, eggs should be removed or the parents relocated. Eggs hatch within 10-20 days, though some may take longer. If hatching is delayed, reducing oxygen levels by stopping aeration or adding organic material may help trigger hatching.

BP: Annual killifish are relatively easy to breed since they instinctively spawn before their short lifespan ends. Non-annual killifish may present challenges due to hatching issues, but these can often be resolved by controlling oxygen levels.

R: Many killifish species exhibit localized color variations, resulting in multiple "races" within a single species.

DC: The difficulty of care depends entirely on the species.