Care Level : Easy, good first fish for freshwater fish beginners

Size : 2 inches (5 cm)

pH : 7 – 8

Temperature : 65°F – 77°F (18°C – 25°C)

Water Hardness : 10° to 25° dH

Origin / Habitat : Central America

Lifespan : How long do they live for? This depends on a lot of different variables (food, aquarium water parameters, etc), but on average they live for 2 – 3 years.

Temperament / Behavior : This is a good tropical fish for the beginner. A common question on the forum is “are platies aggressive”. In general, they are a very peaceful fish. Males might pester females and it can be a good idea to have two females for every one male. Doing this will prevent the male from harassing a single female.
Another common question is “what kind of fish can live with them?” The answer to that question is: many! Mollies, swordtails, various tetras, etc. Just keep in mind the male/female ratio.

Breeding : They are livebearers which means that the babies can swim immediately after birth. Usually, not much effort is required to get them to breed. If you have a male and a female, chances are they will breed. The parents must be separated from the young after birth. For more information on breeding them, please read the breeding livebearers article. That article talks about guppies and swordtails but the process is similar with Platies.
If you want to try and raise the fry, get a breeding box or breeder net like these:

Breeding Box or Breeding Net

Breeding Frequently Asked Questions (credit: aylad on the Fishlore forum) :

Is my platy pregnant?

Yes. Easy question. If the following are all true, she is most likely pregnant:

1. She has been in a tank with a male or swordtail within the last 6 months.
2. She is an adult, more or less (rough estimate, maybe 3/4 of an inch long).
3. She is a she. See the gender ID section on this page.

When will she drop her fry (give birth)? Or how long are they pregnant for?
Platies normally stay pregnant for roughly a month. Having said that, the water chemistry and temperature in your tank may shorten or extend the pregnancy, and if they pregnant platy is heavily stressed out due to the water chemistry, incompatible tank mates, or similar reasons, she may terminate the pregnancy. If you don’t know how long she’s been pregnant, it’s not always easy to give a simple answer to this question. The classic sign is a large, dark “gravid spot” above and slightly in front of her anal fins; she may also “square off,” which means to have a somewhat square-shaped belly. Younger platies, however, may not square off noticeably, and certain color patterns may make the gravid spot harder to see.

In any case, if she squares off, she’s ready to start dropping fry any second now. If the other fish are chasing her around the tank, she may already have started giving birth. When her fry start dropping, the other platies will tend to see her as a vending machine with fins, dispensing free snacks. See “will the other fish eat her fry” below.

How many fry will she drop?
Again, it’s hard to say, because depending on her age, health, water conditions, how many times she’s given birth, etc. etc. etc., it may be 3-4 or 30-40. Leave mom in the breeder net for 6-12 hours, although she probably won’t take that long.

If your breeding container doesn’t separate mom from the fry, she might be able to eat some of her little babies during this time period (I’ve read that she won’t eat them for a few hours after giving birth, but I have seen them swallow a fry IMMEDIATELY after birthing it. Its total lifespan was less than 5 seconds). If you see as many fry in the breeder as you want (or can take care of), go ahead and move her back into the tank. If you miss a couple, well, she’d probably have eaten at least that many anyway.