Swordtail Basics

KingOfSwords · 04-20-2005, 08:01 PM

The Swordtail, usually identified as Xiphophorus helleri, is one of the most popular of the livebearing fish in the hobby today. Along with the two species that are sold as "Platies", they come from a genus that is widespread throughout Mexico, and into Guatemala and Belize. Swordtails are primarily found in rivers and streams, though some populations also occur in large lakes. Therefore, good water quality is of great importance for their continued health and well-being.

Like most of the common Livebearers, they prefer moderately to very hard water. Swords are better off at lower temperatures than one might think, from about 68 to about 74, though they will live quite well up to about 82. To keep them properly requires a minimum of a 30 inch long tank, and a good cover, as they are excellent jumpers. Some algae in their diet seems to help the color, and keeps them healthier. However, they will also eat anything that happens to come within view; flakes, pellets, frozen, and live foods are all taken with gusto.

Swordtails can attain a much greater size than normally seen in the hobby. Most stores carry 3 inch body size fish as "large", but in the wild they can reach 6 inches! There are some related species that get even larger.

Mature Male Swords are easier to sex than other livebearers, because they have the obvious extension of the lower part of the tail (the "Sword") in addition to the usual modified anal fin, or Gonopodium. In the wild, males defend a territory, trying to mate with the schools of females that enter it, and chasing away rival males. These territories can be quite large, so keeping more than one male in the average aquarium is not recommended. Only in larger tanks will additional males be safe.

There are many color varieties of Swordtails in the hobby today, as well as a couple of fin types. Much of this comes from crossing the original species, Xiphophorus helleri, with other species of the same genus, especially X. maculatus, the common Platy. The fact that they will readily interbreed should be remembered if one is considering combining the two species in a community aquarium. Crossing with Variatus Platies, X. variatus, can also occur.

Attached photos are a Red male and female for comparison of sexes, and a 4 inch body Black Hi-fin Lyretail Sword to show what careful breeding can produce.

MikeR · 04-20-2005, 09:24 PM

K o' S:

Great information!

I've seen some swordtails with rather crooked swords. Is this a genetic or water-quality issue?

Mike

KingOfSwords · 04-20-2005, 10:07 PM

Deformed swords aren't usually genetic, most of the time it is the result of overcrowding. This is partially a water quality issue, and partially intraspecific aggression. Male Swords are very territorial, and the "sword" is the banner with which they attract females, who are also attracted to larger males. That makes it a prime target on a rival. Small males often are attacked, not only by larger males but also by females. The sword takes damage, and if conditions aren't clean enough, it will grow back crooked. If there's a "kink" or two in the sword, it's probably for this reason, and not genetic. It is a similar condition to poorly shaped ventral filaments on Gouramis, which often have multiple kinks from various injuries.

MikeR · 04-21-2005, 09:41 PM

That's what I thought. It seemed to me that I saw more of the crooked sword syndrome in over-crowded tanks.

Mike

Sajica · 04-26-2005, 07:47 PM

I love the Black Hi-fin Lyretail Sword. Would it be possible to get some from you? Like a bunch?

KingOfSwords · 04-26-2005, 10:13 PM

Not that fish, that was shot at the ALA convention, he's not mine. If he were, I'd have to try artificial insemination, since he's lyretail.

Lyres are "functionally sterile", they can't breed because the gonopodium is severely deformed. People used to try cutting it off (OUCH!

) but there are structures at the end of a normal gonopodium needed to "catch" the vent of the female, and those aren't there on a "circumcised" male lyre. Recent A.I. experiments in Hawaii have proven that Lyre isn't fatal when homozygous, as was believed back in the late '60's/early '70's. So, homozygous lyretails have been produced, and a female of that genotype will produce 100% lyres even if mated to a normal male. (In which instance the fry are all heterozygous again.)

I do believe someone in the area of Lansing, MI, has been producing the same strain as was in that shot.

Sajica · 04-27-2005, 07:07 AM

Man, you really are a livebearer expert. Interesting information.

Rhodophyta · 12-15-2005, 07:35 PM

I have a young trio now of the sword that has orange on the front and back thirds of the body, and a white band across the center. I am told there are two distinct mutations that cause this pattern, and they can be distinguished from each other by differences in the patterns. Does anyone know how to tell which one I have?

KingOfSwords · 12-15-2005, 08:21 PM

The strain you have is commonly called Koi Swordtail, and is variable to some degree. Another strain, known as Peppermint, also has areas of red and white, but there are certain differences. The koi has clear delineation of the red and white areas, while the Peppermint has more of a fade from one area to the other. One thing all Koi Swords have in common is that the head is red, with the back edge of the red zone angling backward from bottom to top.

Koi can also be found under two other names: Santa Claus, which has the three large color zones like your fish; the other is named after a white Koi carp with a red head (forgot the name, Kohaku maybe?). The second has just the large red zone at the head, and the remainder of the body is almost all white, though a few red spots and streaks may appear around the caudal peduncle on some fish. Both these forms come from the same spawns, I have not yet learned if each can be inherited separately or if they are just variable expression.

I've been working with those fish a little over a year now. I have gotten one spawn of 6 fry. The female was the red headed type, while the male was a very nice tri-zoned specimen. Of the few fry I found, five were tri-zoned, with only one out of 6 showing the red head only like its mother. Even at that, the tri-zoned fish are extremely variable in the width of the white band in the center.

KingOfSwords · 12-15-2005, 08:21 PM

The strain you have is commonly called Koi Swordtail, and is variable to some degree. Another strain, known as Peppermint, also has areas of red and white, but there are certain differences. The koi has clear delineation of the red and white areas, while the Peppermint has more of a fade from one area to the other. One thing all Koi Swords have in common is that the head is red, with the back edge of the red zone angling backward from bottom to top.

Koi can also be found under two other names: Santa Claus, which has the three large color zones like your fish; the other is named after a white Koi carp with a red head (forgot the name, Kohaku maybe?). The second has just the large red zone at the head, and the remainder of the body is almost all white, though a few red spots and streaks may appear around the caudal peduncle on some fish. Both these forms come from the same spawns, I have not yet learned if each can be inherited separately or if they are just variable expression.

I've been working with those fish a little over a year now. I have gotten one spawn of 6 fry. The female was the red headed type, while the male was a very nice tri-zoned specimen. Of the few fry I found, five were tri-zoned, with only one out of 6 showing the red head only like its mother. Even at that, the tri-zoned fish are extremely variable in the width of the white band in the center.