When you decide to get a guinea pig, it is important to provide housing for him, before you bring him home. Not just any old cage or housing will work for guinea pigs. It is important that they have plenty of space, and that their space is safe and comfortable for them.
Unfortunately, most of the commercially sold cavy cages really aren't adequate for guinea pigs. Most breeders and experts recommend designing your own cage, to ensure that the pen has plenty of room. Ideally, you will provide 10.5 square feet for two guinea pigs, and approximately 7.5 feet for one guinea pig. You should absolutely avoid the use of wire flooring in your guinea pigs pen.
The first thing you want to do is build the sides of your pen. The best thing to use for this is chicken wire. Note that guinea pigs will chew wood, and while they may gnaw on plastic, they cannot destroy hard plastic very easily. Really think about the materials that you will use for your guinea pigs pen, and look on the Internet to see the materials and designs that other guinea pig owners have used.
It is very important that you not use wood for the floor of your pen. Odors, including odors from urine and feces, will soak into the wood, and it won't take long before you have a smell in your house that you cannot get rid of. Plastic is preferable, because it can be washed, and the odor won't seep into it.
Once your pen is ready, it will need bedding. You must avoid bedding that is made of cedar and/or pine shavings, as these can be harmful for your guinea pig. Instead, choose Aspen shavings, newspaper bedding, or pellet bedding. Top this with fresh hay, and be prepared to change the hay at least twice a week, and change the bedding weekly. Bedding can be spread over the entire surface of the pen.
Next, you need toys and other accessories. The important thing here is not to place items against the sides of the pen, as this will prevent the guinea pig from running around the interior. He needs to do this for exercise, and he will do it often - unless his pen is too crowded for running.
The first thing to add to your guinea pigs pen is a hiding place. Guinea pigs love to hide, and hiding places can easily be constructed from numerous materials. The best hiding place is a plastic tub, turned upside down, with a little door cut out. Avoid using cardboard, as it will have to be replaced often.
Your guinea pig wants more complex hiding places as well, such as tunnels. You can purchase different tunnel systems at any pet store, or make your own using PVC pipe and PVC joints. Make sure that there is plenty of airflow. Finish your guinea pigs home with a ceramic water bowl, a pet bed, a water bottle, a hay hopper, and plenty of toys that he can safely gnaw on.