Platies (Xiphophorus maculatus) are colorful liverbearers that are easy to keep in an aquarium. They belong to the family Poecilidae, which includes the guppies and swordtails. In fact, platies belong to the same genus as swordtails. Most platies that you find today have swordtail genes in their genome because they interbreed often.
Platies are from Mexico. Both the male and female of this species are similar in coloration, however, the male has a modified anal fin called a gonopodium. Platies engage in internal fertilization and the male platy uses the gonopodium to transfer sperm into the female.
Close-up of Male Platy Gonopodium
Females of this species are slightly larger than the males (about 2-3 inches or 5-7.5 cm in length). Platies come in a variety of colors: orange, red, yellow, blue, white, or sunburst. A lot of platies have some black on their body, fins, or tail.
Platies are omnivores and readily eat dried food, such as dried tropical flakes, and they will also eat insects, tubifex worms, bloodworms, small crustaceans, such as brine shrimp, and plant matter.
Platies are peaceful fish that can be kept in a community tank.
They prefer neutral to slightly alkaline water (pH of 7.0-7.3) and the water temperature should be between 72-79 degrees Fahrenheit or 22-26 degrees Celsius.
As with any livebearing fish, it is best to have at least 2-3 females per each male because male livebearers often harass the females. Plants are also good so that the females have plenty of hiding spaces.
Like any livebearing fish, platies are easy to breed in an aquarium. Spawning will occur in a community tank. All you really need to do is to put a male and female fish together. You can also interbreed them with swordtails (Xiphophorus helleri).
It is sometimes difficult to tell when your female platy is pregnant. This is because not all female platys have a gravid spot. In the females that do have a gravid spot it tends to get larger as the fry grow larger.
Platy fry are born fully developed in approximately four weeks. There is no parental care of the fry. The parents may eat the fry and so it is best to separate the fry from the adults if you want them all to survive.
If you are unable to keep the fry separate, having lots of hornwort in your tank (both floating and planted) will help to protect the fry.
You can also use a breeding trap. These are inexpensive and are available at most pet stores. Breeding traps are plastic containers that you put the pregnant female in (or any livebearing fish). Don't put the female into the trap until she is close to giving birth. The breeding trap floats in the aquarium. The trap is separated into two compartments. The top compartment houses the pregnant female platy. There is a small space between the top and bottom compartments so that the fry drops through to the bottom compartment where their mother can't reach them. It is possible for the fry to swim back through this space into the top compartment, but they usually don't. After the female has finished giving birth to the fry you should remove her from the trap and place her back in the aquarium. The plastic piece that separates her from the fry should be removed from the trap and you can raise the fry for a short time in the trap. However, the water in the trap tends to get somewhat stagnant and so this isn't an ideal place to raise the fry for long. If you do raise the fry in the trap you will need to clean out the trap and replace it with water from the aquarium on a regular basis. It is best to raise the fry in their own aquarium. Because they are so small they can easily be raised for awhile in a 5-10 gallon tank of their own.
Keep in mind that female fish tend to find confinement to the breeding trap very stressful. If you have another aquarium it is best to place the female in it (and have no other fish present). Make sure it has lots of hornwort so the female fish won't eat her fry. As soon as she is finished giving birth to the fry, then you should place her back into the main aquarium. Then you have the fry in an aquarium of their own to raise them in.
Feeding the Fry
Platy fry can be fed newly hatched brine shrimp, newly hatched daphnia, or they can be fed powdered fry food for livebearing fish. You can find these online or at your pet store. I've successfully raised baby platies to adulthood using dried fry food, however, you are going to get better growth of your fry if you feed them live food as well as the dried food. Don't try to feed them flake food for adults because the fry are too small to eat them.
For more information on feeding platy fry see the article Feeding the Fry of Livebearing Fish.