http://elmlaneaquatics.com/fish/tropical/livebearers/

Guppy (Poecilia reticulata)

Guppies must be the most popular of all home aquarium fish.  The males are often beautiful, with a wide variety of brightly coloured tail fins; the females usually less spectacular looking, but still nice little fish.   They are ridiculously easy to breed, and it’s fairly certain that if you have a mixed tankful, you will very soon be overrun, even though the parents will eat their own (live born – not eggs) babies unless there are lots of hiding places, or unless you remove newborn fry and keep it in a separate fry tank until it’s big enough to fend for itself with the grown-ups.  You can, of course, keep a tankful of males alone (they won’t fight or bicker about dominance) or a tankful of females, into which you just introduce a male now and again to keep the herd replenishing itself.
You can tell if a female guppy is pregnant by observing a dark area (gravid spot) on the underside of its belly, just in front of its tail, and the fact that it’ll probably slow down and start hiding in undergrowth.  You can then, if you wish, remove the mother-to-be into a breeding trap which floats just under the surface of the tank, until she gives birth. Females can store sperm for months, so don’t be surprised if you get babies in your female only tank: if she has, while in the shop, so much as looked at a male guppy, chances are she’s already pregnant when you buy her. Commercially bred guppies often do not have very long life-spans, though well looked after they can live for a couple of years.  Do make sure, however, if you plan to keep a mixed tank, that that the males will literally pester the females to death, so make sure you have many more females than males (3 – 1 female to male at least).

They will eat most fish food: frozen, freeze dried and live foods, as well as flake food.  Try and give them a mix, in order to keep them at the peak of health.  They will live happily in a community tank with other live-bearers or with other small community fish such as danios and tetras.  They are best avoided around slower moving, shy fish, as they are very active and could stress them out.  Some sources say they can be kept with angel fish, but larger angel fish are most likely to view them as a tasty treat.

Size (fully grown): 4 – 6cm (1.5 – 2.5″)

Water temperature: 19 – 29C (optimum 23 – 24C)
Water pH: 6.5 – 7.5