Guppies are among the easiest fish to breed. A female gives birth to 20 to 30 babies at a time and can give birth for several months after one mating session. The small guppies, when left to fend for themselves in a tank with other fish, often are eaten by the adult fish. To avoid losing your guppy babies to the older fish, it is important to separate them from the rest of the tank. The best way to do this is to set up a special breeding tank.
Fill a 5- or 10-gallon tank with water, and add two to three drops of dechlorinator per gallon to remove harmful chemicals.
Place the plants into the tank. They will most likely float because there are no rocks in the bottom of the tank to hold them down, but this is OK. The purpose of the plants is to give babies a place to hide.
Install the sponge filter to keep the water clean.
Attach the heater to the inside of the tank. The heater should be set between 25.6 and 27.8 degrees Celsius for best results.
Place the female in the tank as soon as you notice she is pregnant. You can tell a guppy is pregnant when her abdomen begins to expand. You can also place the female and male into the breeding tank and then remove the male when the female shows signs of pregnancy.
If you do not want to set up a completely separate tank, install a divider in your tank to keep the breeding area separate from the other fish.
Remove the female from the breeding tank after the babies are born if you do not want her to eat any of the offspring. However, she probably will give birth again in about a month.