Care
The Dark-edged Splitfin is known from the upper Rio Lerma basin and the Zempoala lagoon in Morelos, Mexico. This goodeid species lives in quiet, cool, shallow waters over silty or muddy substrates with algae-covered rocks and an abundance of plants such as
Lemna (duckweed),
Nasturtium (watercress),
Potamogeton, and
Salvinia (floating fern). The aquarium should be mature and well-filtered, with plenty of shady areas provided amongst aquatic vegetation and décor such as spindly driftwood pieces and rocky caves. This is a fairly peaceful species that is best kept in a species tank environment, with 2 or more females to every male; this will reduce the amount of attention that any one female receives from the amorous males and will also further your chances of raising more fry. A shoal of at least 6-8 fish is preferable in a good sized tank, and although there may be a bit of minor chasing between rival males, they are rarely aggressive towards one another and generally do not cause damage. Tankmates are possible, but do ensure these are short-finned, fast-swimming, and are happy in the same cool conditions - although be aware that in such a community setting, the Dark-edged Splitfin fry may be at risk from predation. Be sure to keep the temperature cool as these fish do not fare well above 22 °C (72 deg F); a means of chilling the water may be necessary during the warmer summer months. Interestingly, the males of this species are capable of displaying a dark spot in the same area that you would expect to see a gravid spot on the females. A study found that it was largely sub-dominant males that displayed this marking, and it is thought they may use this to blend in and gain access to protected groups of females in order to reproduce. Unfortunately, the Dark-edged Splitfin is listed as Vulnerable on the IUCN redlist for endangered species - as sadly it has disappeared from many of its known historic sites over the last century, and remaining populations are often small and isolated. The future of this species is decidedly uncertain. The fish pictured here were commercially bred in the Czech Republic. May also be seen on sale as Golden Sailfin Goodeid.
Feeding
Flake, micropellets, small frozen foods such as mosquito larvae, daphnia and vitamin-enriched brineshrimp, plus vegetable matter such as green flake, lettuce, spinach and kale.
Breeding
These fish will reproduce in any well-kept aquarium, and this is usually initiated by the males, who will flash their showy finnage in front of the females. The male fish fertilises the female by the use of his andropodium, and after 55 days, the females can be expected to release 10-20 (occasionally as many as 30) live young. The adults are not usually a threat to the young, which may be as large as 8mm SL when born; however, do observe them carefully. A heavily planted aquarium will usually provide enough hiding places and negate the need for separation of adults and young. Not surprisingly, the total number and size of fry will depend on the size of the adult female, and she will appear quite hollow bellied after giving birth.
