Guinea pigs are social animals that prefer to live in small groups. Any group of female guinea pigs will likely become great friends, but it is harder to get adult males to bond unless they are from the same litter. You should not keep male and females together, as guinea pigs multiply quickly.
A cavy that lives indoors should be kept in a solid-bottom cage with a wire cover. Never use an aquarium, as that enclosure will not provide adequate ventilation. At the very minimum, each cage should provide at least 4 square feet of space per guinea pig, although the larger the cage, the better for the guinea pig.
Cages should be kept away from drafts and extreme temperatures in a room that is maintained between 60 and 80° F. They should be lined with bedding made of aspen or hardwood shavings, timothy hay, or processed paper products. Do not use cedar or pine chips as bedding, as they can be toxic for the animal.
Cavies also like to have a cave to sleep in, such as a medium-sized flower pot or a covered sleeping box. Indoor guinea pigs should be taken out of their enclosures regularly to exercise and socialize, and in warm weather, they should be exposed to direct sunlight for 20 minutes at least 2-3 times per week.