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KILLIFISH




KILLIFISH

Killifish fare widespread throughout Africa, Asia, South America, North America, and parts of Europe. These fish almost every biotope in freshwater. More than 500 species are represented in this group. Several species also inhabit brackish water and a few actually live in pure salt water. Killifish are well-known for their adaptability and many species inhabit bodies of water that dry up during the dry season. Some species spend part of the year living under a layer of ice, while the Desert Pupfish (Cyprinodon species) has, on occasion, been found in water with a temperature of 116.6°F (47°C). This is remarkable considering that this temperature is well-above the lethal body temperature for nearly all vertebrates (McGinnis 179). Since Killifish come from a range of environments, adaptations have been made.  Among the most famous is the 'phoenix-like' cycle of death and rebirth.

Killifish included in this work:

SIZE: Most Killifish are small, ranging in size from 2 to 3.5" (9 cm). Only a few species exceed 8" (20 cm).


 


TANK: For most species a tank measuring 24" (41 cm) with a capacity of 10-20 gallons (38-76 L) is more than sufficient for a pair. Although Killifish inhabit a range of habits, most are usually at home is a shallow tank with little or no water circulation. The tank should be well-planted with some shading provided by some floating plants. The gravel should be dark and hiding places should be arranged with wood, roots, and rocks. Use a tight-fitting cover as many species leap for flying insects in nature. 


 


WATER: The water values depend entirely on what biotope that the species inhabits. MostAphyosemion species can be kept in water with a pH from 5.5-7.0, a water hardness from 3-10 dH, and a varying water temperature. Aplocheilus species prefer water with a pH from 6.0-7.5 and a water hardness from 3-10 dH. Cynolebias,Epiplatys,Nothobranchus,Pachypanchax,Pseudepiplatys,Pterolebias, andRivulus species require water with a pH from 6.0-7.0 with a water hardness from 4-12 dH. Lamprichthys species require more alkaline water with a pH from 7.5-8.5 and a water hardness between 10-20 dH. Many species are maintained in water that is too warm.  Thus it is important to read the individual descriptions of each fish to find the proper temperature. 


 


SB: Despite their small size, many male Killifish are pugnacious and aggressive towards one another. It may be best to keep only one pair of a species per tank so that males do not quarrel.  In a large tank, two or more pairs can be kept, although plenty of retreats should be provided. Killifish are usually fairly good community fish when combined with other small, peaceful species that can exist is similar water conditions. 


 


SC: Most Killifish are suitable community fish, although what species they can be combined with depends on the species of Killifish in question. For example, Aphyosemion species and kin from West Africa can be combined with other small fish that thrive in slightly acidic, soft water. Such fish include South American tetras, hatchetfish, pencilfish,Corydoras, and Loricarids; AsianTrichopsis,Pangio, andPuntius titteya; and African small characins and some Mormyrids. For other Killifish, please see the species descriptions.


 


FOOD: Surface dwelling Killifish, often those with an obvious up-turned mouth, feed primarily off of small flying insects. Fish of other swimming levels usually feed off insect larvae, small aquatic insects, and small crustaceans. Bottom level species consume river worms, crustaceans, insect larvae, and aquatic insects. In aquaria, Killifish will eat most live foods as well as flake foods once they are acclimated.


 


SEX: Usually the sexes are very easy to distinguish from one another. Males generally are far more colorful than the females.


 


B: As an adaptation to their environment, Killifish have developed interesting spawning behavior.  Most Killifish fall into one of two groups; 'annual' and 'non-annual' fish. Among these types, two main spawning methods are practiced: bottom spawners and substrate spawners.


'ANNUAL' KILLIFISH 

For most species a small breeding tank of 5.5 gallons (21 L) is fine for a single pair. Use a substrate of fine sand or preferably, peat moss.  Another possibility is to furnish the tank with containers having lids. A 1" (2.5 cm) diameter hole can be cut in the side of the container near the top and peat moss can be used as a substrate in this container. The pair should be conditioned prior to being introduced into the tank. After the pair spawns, the peat moss can be removed carefully and placed in a plastic bag or container where it should be stored around 77°F (25°C). The moss should be stored for the recommended amount of time, usually about one to four months. After the storage period, the moss can be placed back in the spawning tank.  The fry should slowly begin to hatch over the period of several weeks depending on the species. Start feeding the fry as they emerge withDrosophila,Artemia nauplii, and Infusoria.

In nature, 'annuals' are Killifish which inhabit bodies of water that completely dry up. These fish have a short life span, only surviving as long as there is still water in their pool. But, before the adult Killifish dies, they bury their eggs in the mud of their body of water.  The tough-shelled eggs, survive in the mud, and hatch when the rains come. The development of the embryos is affected by ecological factors including temperature and moistness. The embryos stop developing after developmental stages and wait at a period of suspended animation, known as a diapause, until another environmental 'trigger' can   start the  next stage.  Since the eggs are buried at different levels in the mud, and the embryos have different developmental rates, the eggs do not all hatch after the first rain. This ensures that if the rain was a 'fluke,' with no more to follow for a period of time, that some slow-developing eggs would survive until a period of constant rain, later in the season. 

'Semi-annuals,' as someAphyosemion,Epiplatys, andProcatopus species exist, have eggs that can survive periods above the water.  These fish attach their eggs to plants and rocks near the water's surface. Through a series of developmental stages, followed by diapause, the eggs continue to survive for extended periods of time. When the rains return, and the water level rises, the eggs are once again submerged. These usually hatch at night as less oxygen is present in the water because of the respiration of plants. The hatching of many Killifish eggs is triggered by a lack of oxygen.


'NON-ANNUAL' KILLIFISH 

In a well-planted tank, a pair is likely to spawn, although they will eat their own eggs. To avoid this problem use a spawning mop or related substrate as a spawning site. Remove this or the parents after spawning is complete.  The eggs will hatch after a period of 10-20 days, depending on the species. The eggs can be kept in a moist areas for a few days if necessary. Sometimes aquariasts experience problems with the eggs not hatching. Usually this can be attributed to an abundance of oxygen, as Killifish eggs are triggered to hatch by a lack of oxygen. Turn off the aeration.  If this does not do the trick try sprinkling small amounts of powdered food on the surface of the water. By "feeding the water," small Infusoria develop and use up the remaining oxygen present in the water. In nature, 'non-annuals' live out life more like other fish.   


 


BP: 'Annuals' are fairly easy to breed as they have an instinct to spawn before they die.  Some experience difficulty with the eggs of non-annuals hatching. This problem can be solved by the method mentioned above. 


 


R: Many 'races' of a Killifish species may be distributed in a small region. This causes many color and pattern forms to be available.


 


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

By Rhett Butler







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