Platy

A Beautiful Little Livebearing Fish
There are two species of Platy, Xiphophorus maculatus, and Xiphophorus
variatus. Platys are closely related to Swordtails, Xiphophorus
helleri. Xiphophorus maculatus will freely interbreed with
Swordtails. The interfertility of Xiphophorus variatus with the others
two species may be less, but hybrids can occur. The Platies and
Swordtails we buy are often not of pure species.
All three species come from Central America. Xiphophorus variatus,
commonly called the Variatus Platy, appears to be able withstand slightly
colder conditions than the other two species, and may be more suitable for an
unheated tank in a reasonably warm house than the other species, but all are
basically tropical fish.
Platies tend to be shorter but thicker than Swordtails.
Platy Varieties
Water Conditions
The platy is a tropical fish and I recommend a temperature of 24̊ C (75̊
F). They prefer harder water with some salt in it but are quite adaptable.
The platy appears to be better able to survive higher Nitrite (NO2)
levels than most fish, but these should normally be avoided for all fish.
Food
The Platy is an omnivore and will eat some algae as well as live food including
Mosquito larvae (wrigglers) and
Daphnia
.
They do well on all normal fish foods.
The Platies below are clustered round a stick on food tablet. These are made by a number of manufactures including Sera and Prodac. The picture is from AKVARYUM GÜNLÜĞÜ.

Companions
The Platy is a peaceful fish and is a good fish for a community tank of small
peaceful fish. It lacks the long fins of the Guppy and is a faster
swimmer, so its companions can include some of the slightly aggressive fish
that you would not put with Guppies. You need to avoid any large,
aggressive or predatory fish.
Suitable companions include Swordtails, Rummy Nose Tetras, Harlequin Rasboras,
Lemon Tetras, Neon Tetras, Flame Tetras, Buenos Aries Tetras, Black Widow
Tetras, Cardinal Tetras, Emperor Tetras, Head and Tail Light Tetras, Glass
Bloodfin Tetras, Glowlight Tetras,
Guppies,
Endlers Guppies, Neon Tetras, Peppered Catfish, White Cloud Mountain Minnows
and Zebra Danios. Not all these common companions are compatible with
each other. Most of these fish will eat baby Platies.
Sexing
As with other live-bearing fish in this family, the male's anal fin is elongated into a gonopodium (An intromittent organ). The female's anal fin is more triangular. The anal fin of the male in the picture on the left is circled in red.

Breeding
Platies are very easy to breed. The ideal sex ratio is probably one
male to each three females. They have live young, and the babies tend to
be vigorous. They will grow much faster with suitable size live food
although they can be raised on commercial dry or liquid fry food. The
water conditions are not critical. The parents, as well as most other
adult fish will eat the babies.
Pest Fish
Never release your pet fish or put them in the position of being accidentally
released. The Platy has the potential to seriously damage fragile
ecosystems.
Sources
I would like to express my gratitude to the following sources of information
about Platies. James Cook University, Fishnote of the Queensland Government,
Platy Care and Breeding, Aquatic Community, FishLore.com, and for the nice
pictures as well as information, to Bay Fish
+
The picture next to the title is a male variatus Platy by Marrabbio2 (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
The picture showing Play varieties is from Endlers Slovakia.
Steve Challis