Fancy guppies have the size of about 1"~1.5". The females are about twice as large as the males. Females are usually pale and somewhat greyish color with perhaps a bit of bright color on the tail. Males however are generally bright color all over, and are bred for almost any color in the spectrum. Males have longer tails than females, and instead of a normal anal fin they have what is called a gonopodium. A gonopodium is a modified, tubular anal fin used to fertilize the females.

Guppies do quite well in a temperature range of 68 to 80 degrees F. However, 76 degrees seems to be best for good health. Guppies will survive in water as low as 60 degrees F.

Guppies are omnivorous, and in nature consume quite a variety of foods. If you've ever seen a humpbacked guppy, the deformity was probably caused by malnutrition rather than genes. Malnutrition also causes small litters, premature birth, and miscarriage.

Just as important as diet, is frequency. It is better to feed more small meals than one big one. I find that with less than three meals a day, the babies don't grow as fast or as big as they should.

Guppies are live-bearers and are very easy to breed. This means that they do not lay eggs, but rather give birth. Guppies reach sexual maturity at about six months of age, though this seems to vary with water temperature. Up until that time all babies look like females, and then in the course of about a week the males will suddenly change color and the anal fin changes to a gonopodium.

Guppies' life span is about 2 years.