Koi Swordtail - Xiphophorus helleri Kohaku

Introduction

Swordtails have always been very popular in aquaria, especially because of its image as a "beginner fish", which survices even one or two faults in maintenance. The purposeful breeding of livebearers is in contrast to simple multiplication rather an advanced topic and also swordtails first show only at optimal keeping their complete behavioral repertoire. To describe these magnificent fish pejoratively as "beginner fish" is not fair. Anyone who has observed the impressive courtship will look at these fish with different eyes than someone who knows them only from a crowded community tank.

Again and again, there are new color varieties and forms. I enjoy especially the koi swordtail, with its high contrast of orange to white, which look in proper light like plunged in color.

The color of the koi swordtail arise from the base color white with normal eye color or from the base color albino with red eyes. Over that, the opaque color red or orange is presented, which covers the base colore in spots. This factor is not normally present in the genome of the swordtails, but are introduced from the Platy (Xiphophorus maculatus). The phenotypic expression is called "Kohaku" by the Japanese, based on the Koi varieties.

Without the red spots this swordtail is called "Platinum". There are also other types of expression, such as white base color with black spots. These swordtails are called "Utsuri", but that is only seen on the basic white color, because with the basic color albino no black spots are shown. Of course, there are swordtails with black and red spots on white base color, which are the "Showa" swordtails. The much sought-after swordtails from this group are called "Tancho Kohaku" - swordtails. They only carry a red spot on their head on a white background. The breeding of Kohaku swordtails shows only in 1% of cases this pattern.

The irregular black spots should be avoided, because they regularly lead to cancer in animals (Anders, 1997). In Platy genom there is a corresponding tumor suppressor gene, that is not available in hybrid fish and therefore can not keep the oncogene under control. That does not apply to normal "Salt and Pepper", "Tuxedo" or "Nigra" genes of swordtails.

Keeping

As the agile swordtail grow up to approximately 10 to 12 inches for group housing an adequate large tank should be provided. I think an aquarium until 80 cm length is appropriate. A social hierarchy is formed, which leads in small tanks to the permanent suppression of the most vulnerable males. To distribute the aggression, at least 5 animals should be kept together. My swordtails are able to avoid each other in the large 500 liter tank very well.

The temperature should be 22 to 28°C, for the varietys better at the top of the temperature range. I keep them at 24 °C, which is well within the optimum range. The swordtail is more a fish for medium hard to hard water (GH 12 to 30) and feel well around neutral ph-values (6.5 - 8.5).

The swordtail lives mainly omnivorous, which means that they take both animal and vegetable food. A balanced and varied diet with different food types especially vegetable and regularly live food supports the vitality of these fish and provoces their impressive and complex social behavior.

Breeding

The reproductive behavior of swordtails is slightly different from other livebearer. The males display to females very active and permanent. During courtship, the males perform a special dance. The female gives birth to up to 180 juveniles. The special feature of the swordtails is that not all males develop with the same speed. There are smaller "early males" and bigger "late mails", which can only be recognized as mails in a later stage. It may even happen that you think to buy females, which turn out to be males.

Other breeding forms

Through many cross breeding with the Platy (Xiphophorus maculatus), there is a wide variety of colors and forms within the swordtails. The Red Swordtail owes its color from the red Platy and the green swordtail owes his dark fins from the Waigtail Platy. There are also forms with long fins such as the Simpson Swordtail. This phenomenon is due to a malfunction of the pituitary, that affects the body growth. In addition to the breeding forms of the swordtails (Xiphophorus helleri) and platies (Xiphophorus maculatus) and their hybrids, there are also two other types, the Montezuma - Swordtail (Xiphophorus montezuma) and the Dwarf Swordtail (Xiphophorus pygmaeus), which are however not maintained very often.