- Scientific Name: Xiphophorus helleri
- Family: Poeciliidae
- Origin: Mexico, Guatemala, Honduras
- Adult Size: 2 inches (5 cm)
- Social: Peaceful, suitable for community tank
- Lifespan: 4 years
- Tank Level: Top, Mid dweller
- Minimum Tank Size: 10 gallon
- Diet: Omnivore, eats most foods
- Breeding: Livebearer
- Care: Easy to intermediate
- pH: 7.0 - 8.2
- Hardness: 15-30 dGH
- Temperature: 64-77 F (18-25 C)
Wagtail swords first appeared in the 1940's, as the result of a cross between a gold platy and a wild Xiphophorus maculatus. The distinctive mark of wagtails are the black rays in all fins coupled with very little coloration between the rays. Also notable is the presence of black on the upper and lower lip. Marigold Wag swordtails display an intense color contrast, having coal black fins and a red-gold body.
In their native habitat this species lives in very clear, oxygen rich, alkaline waters. Strong filtration is advised to maintain high oxygen levels. Water should be moderately hard, in the range of 15-30 dGH.
Optimum temperature for wagtail swords is lower than for many tropical fish. That should be taken into account when considering them for community aquariums. 74 degrees F (23 C) is the ideal temperature for swords, with lower temps being more readily tolerated than elevated temps.
Beyond the water requirements, wagtails are undemanding in terms of the physical aquarium setup. If breeding is planned, the tank should be densely planted to allow sufficient cover for the fry. Either real or artificial plants are suitable
Wagtail swords will readily accept a wide variety of foods. Live foods such as mosquito larvae, tubifex, and daphnia. These live foods provide some vitamins that often are lost in dry foods during storage. Freeze dried foods are also readily accepted, and are good alternatives to live foods. The advantage of FD foods is the reduced risk of disease that may be transmitted via live foods.
Because wagtails possess an intestinal tract that is longer than carnivores, they benefit from the roughage found in vegetables. In addition to flake foods containing vegetable matter, cooked peas, lettuce, or spinach may be used as supplemental foods.
Wagtail swords are primarily top feeders, as is evidenced by their upturned mouth. Foods that fall to the bottom, or that are not eaten within five minutes should be removed promptly to avoid fouling the water.
Wagtail swords are considered ovoviviporous fish, meaning they hold the developing egg until it hatches before giving birth. However the developing fry gets all it's nurishment from within the egg sack, not from the mother.
They also exhibit superfoetation, a process in which sperm are stored within the oviducts of the female. A single mating can result in broods of fry over a period of months or even years.
As one batch of eggs develop, the next batch of eggs begin to ripen. Once the fully develop fry are born, the next batch of eggs can be fertilized immediately using the stored sperm. This process allows for smaller periods of time between births, thus producing more total offspring.
Mating in livebearers requires internal fertilization of eggs. Males possess a modified anal fin called the gonopodium that allows them to transfer packets of spermozeugmata to the female. These packets contain several thousand individual spermatozoa.
Fertilization of the eggs takes approximately two days, and additional sperm are stored in the oviduct to be used for producing future broods.
From the time of egg fertilization it takes approximately four weeks for the fry to fully develop. Subsequent broods will follow at the same four week intervals, however temperature and the length of daylight can play a factor. Longer days and higher temps result in shorter periods of time between broods. Birth almost always occurs at dawn or shortly thereafter. Brood sizes range from 50 to 200.
Adults will eat the fry if they are hungry, therefore it is important to keep the parents well fed. The aquarium should be well planted with live or artificial vegetation, to allow the fry places to hide. Commercial breeding traps are not advised, as they place considerable stress on the female.
Fry require a high protein diet, and should be given commercially prepared fry food or live foods. Freshly hatched brine shrimp is the live food of choice, however frozen baby brine shrimp is a good alternative. Feedings should be frequent and large enough to ensure that all the fry get food.
Water changes and cleaning must be often to avoid the build up of lethal toxins such as ammonia and nitrites. As soon as the sex of the young may be determined, they should be separated to avoid impregnation of the females. Young can begin reproducing as early as three months of age.