Telling the sex of a platy is very easy. In fact, the sex of all livebearers – tropical fish, including platys, mollies, swordtails, and guppies, that produce live young, as opposed to eggs which need time to hatch – can be determined in the following foolproof way.
The most obvious physiological trait that differentiates a male from a female platy is easy to spot …if you know where to look.
If you examine the diagram above, you’ll notice that the anal fin of the male platy (the fin circled in red) looks different from that of the female platy (also circled in red). The anal fin of the male platy is called a gonopodium and looks more clamped, flat, and elongated. The anal fin of the female platy, on the other hand, is noticeably more fan shaped.
And that’s all there is to it! That’s how you can tell the sex of your platy.
Again, not only platys, but also mollies, swordtails, and guppies can be sexed in the way described above.
Well, livebearers breed prolifically in the home aquarium. If you want to avoid producing a continuous supply of baby fish, get only female platys, mollies, swordtails, and/or guppies. Male livebearers tend to be aggressive towards each other and, for this reason, I do not recommend getting only males.
However, male livebearers tend to be more colorful than their female counterparts (this is especially true of guppies), so you may want to mix some males into your female population. Needless to say, this will produce offspring.
If you choose to go this route, I strongly advise a livebearer ratio of one male for every two females. If, for example, you have two male mollies in your aquarium, you should also keep four females with them. Doing so will simultaneously curtail aggressive male competition and distribute (and, hence, attenuate) the physical stress of carrying babies among the females.
In other words, a ratio of one male to two females will lesson the stress felt by the females by distributing the “special male attention” that the females receive among more than one fish.
Here again, we see that establishing a balanced aquarium environment is key to successful tropical fish keeping. Indeed, aquarium care is simple when you understand the basic needs of your fish.