OWNING TROPICAL FISH - THE LIVEBEARERS / SWORDTAILS
The Livebearers - Swordtails
In the same ggenus as the platies is the swordtail, Xiphophorus helleri. The platies and swordtails interbreed easily, to the point that many strains of both species have been heavily hybridized, with consequent erosion of the differences between them. Still, it is very simple to distinguish between a platy and a swordtail if the fishes you use for comparison are at all true to their original type.
Good male swordtails are the designer models among the livebearers, long and low and sleek-looking in contrast to their chunky relatives and most other tropicals. The "sword" extending from the tail of a nicely shaped male is a truly distinctive feature, a touch of pure elegance. Even the most jaded hobbyist can summon up enthusiasm for a tankful of good swordtail males. They are classy fish.
Like the platies, swordtails come in many colors. The basic colors are green and two forms of red, brick red and velvet red, but those old standbys now coexist with golds, albinos, pineapples and many others. Again like the platies, swordtails also exist in long-finned forms. Possibly because they are over-all bigger and more streamlined, swordtails seem to benefit more in appearnce than do the platies from all of the fin-lengthening and veiltailing and lyretailing they've been through - but that's for you to judge.
Swordtails (the males more so than the females) are jumpers, so keep a tank housing swordtails well covered. A thick layer of floating plants will tend to cut down on the aerial acrobatics, but don't count on it as a sure cure.