Most modern varieties of platy and sword are the result of hybridization, and I would doubt there are many "pure" strains (i.e fish that, genetically speaking, are 100% swordtail or platy). Crossbreeding is therefore a real possibility and if you want to maintain the integrity of any strain you keep, you must keep it isolated from all other strains of sword or platy.

Often, whenever a new color or pattern emerged in one species, breeders would transfer that novel gene into the other. For example, I don't recall seeing mickey mouse swords years ago, but they are everywhere now, and i suspect the "mickey mouse" gene was bred into swordtail lines via platies. Probably the neon sword is already the product of of a platy/sword cross. Swords used to be much larger fish than they are today, and I believe some of the reason they are now smaller is a result of platy genes.

 

Interesting stuff. The two swordtail females appear pretty pure when compared to default generic images of neon swordtails. The two males (platy and variatus hi-fin) have left them alone so far minus one instance.

 

Yes, Platys and Swordtails might as well be the same species the way they crossbreed. It takes some work and tank space to ensure strain purity.

 

It is fascinating. I wish someone would write a really good book on the history and development of sword and platy varieties. Some have been around forever, and some are very new. But it seems like everytime there's a new strain of platy, it's only a matter of time before you see a similar strain appear in swords.


It's tough to tell visually regarding their purity. Usually, upcoming broods of young tell the story.

If you want to breed a "pure" strain of any livebearer, you'll have to start with breeding stock you obtain from someone who is a specialist in them. Females need only mate once in order to give birth numerous times from that one mating. So the femaled you obtain must either be unmated, or mated exclusively to males of their strain.

In any case, you can buy them from the "Assorted Swordtail" tank at the local PetCo!