The common name “Platy” is derived from the original generic family name of this fish, Platypoecilus (which later became Poeciliidae). In reality, Platies stem from two related species of freshwater fish in the genus Xiphophorus, namely X. hellerii and X. maculatus, both of which are native to an area of North and Central America stretching fromVeracruz andMexico, to northernBelize. Both species are livebearers, similar to other fish of the family, such as the guppies and mollies.
The two species, the southern platyfish and the variatus platy, have been interbred to the point where they are difficult to distinguish. In fact, most platies now sold in aquariums are hybrids of X. hellerii and X. maculatus. The southern platyfish, is sometimes also known as moonfish or mickey mouse platy. While wild varieties are drab in coloration, lacking the distinctive dark lateral line common to many Xiphophorus species, breeders have developed a multitude of colour varieties, for example, orange, red, yellow, red/black, and black/white. Nowadays there is even albino platy with red coloured eyes, as well as mottled and marbled ones. Color and fin shape also vary wildly in the aquarium trade. Curiously, in general, if the male has a sword-shaped tail, they are called ‘swordtails’! Otherwise, they are labeled ‘platy’.
Platies grow to a maximum overall length of 6 to 7 cm. Sexual dimorphism is slight, but the male’s caudal fin is more pointed. Also, the anal fin of the male has evolved into a gonopodium, a stick-shaped organ used for reproduction. The female anal fin is fan shaped.
They are omnivorous, and their diet includes both plants, as well as small crustaceans, insects, and annelid worms.
IN THE AQUARIUM
Because of their hardiness, Platys are easy to keep and are well suited to a community aquarium, provided there is lots of space. They prefer water with a 7.0–8.0 pH, a water hardness of 9.0–19.0 dGH, and a temperature range of 18 to 25°C (64–77°F). In terms of tolerance to high nitrite and nitrate levels, they can withstand fluctuations much better than any other fish and because of that, platies are always used as starter fish for a beginner’s tank.
Breeding platies is rather straightforward and most of the time, it will happen on its own without your intervention, provided the living conditions are optimal, with good water quality and a large tank space area. A common statement in the trade is that it is harder to stop them breeding, than to make them do so, with “surprise” fry appearing in community tanks regularly.
The breeding ratio is 1 male to 3 females. This ensures that there is no in-fighting, nor will the male chase a female to exhaustion. Being live-bearers, these fish do not lay eggs, but release live, free swimming fry. Pregnant female platies are easily identifiable by the size of their bellies and the darkening of the gravid spot right above the anal fin. Usually the gestation period is around 28 days, after which the female gives birth to about 20-40 young at a time.
Be warned though: Platies are notorious for eating their own babies and in order to ensure that the fry have high survival rate, they either need heavy planting, or alternatively, need a planted breeding tank from which the mother can be removed!
Caring for platy fish fry is extremely easy. At birth they are between ¼ to ½ cm. long and already active little swimmers, which will immediately dash off to a hiding spot. They will also avoid any movement, or any object approaching them. The fry will readily accept any small foods offered to them – usually powdered flakes, liquid fry foods and such, but for their health and well-being, brine shrimp nauplii should be a major part of their diet.
Finally, the fry reach maturity in just three to four months – after which they are then ready to breed themselves!