If you think that housing a guinea pig is as easy as putting it into an aquarium, think again. Certain types of cages are actually bad for piggies because they don't provide enough space or have other drawbacks. It's important to choose appropriate housing for your cavy.
Aquariums were once a common way to house guinea pigs, and unfortunately they're still quite popular with people who don't do research before buying a cavy.
At first, an aquarium might seem like a good choice because it's relatively cheap, solid (as long as you don't drop it, since it's made of glass), and easy to clean. Unfortunately, its solid sides mean the poor guinea pig inside doesn't get any air circulation.
Aquariums are also much too small for a single guinea pig. Cavies are social animals that do best when you keep two or more together, which means an even worse situation for the animals if you house multiples in an aquarium. Even though most guinea pigs enjoy being with other members of their species, they'll fight if their quarters are too small.
One last problem is the fact that the solid glass muffles sound in the aquarium. A guinea pig who gets used to that environment may be skittish if you take it out and it's suddenly bombarded by unmuffled noise.
Pet stores sell a wide variety of cages labeled as being good for guinea pigs. Unfortunately, most don't meet the minimum recommended size of 7.5 square feet for one guinea pig and 7.5 to 10.5 square feet for a pair.
Beware of cages sold as "starter homes," which usually means cheap and small. There are some larger cages, like the Living World Deluxe Extra Large Habitat, which is what I bought for my first guinea pig, but they're still below the ideal size.
Many commercial cages have ledges, but those don't count toward the square footage. They're handy spots for food, and I hang my piggies' water bottles over their shelves so it doesn't drip on their bedding, but it's not actual "living space."
If you decide to get a pet store cage for your guinea pig, you'll have to spend a lot of money to get one in a decent size. You might even need to get two and join them in some way. However, even if you link two cages to make a habitat with enough square footage, your guinea pigs will won't be able to run around the entire cage space unimpeded.
Cages made from storage cube grids and Coroplast, a type of corrugated plastic used in sign making, are the gold standard of guinea pig housing. They give piggies a lot of room to roam, and many people line them with felt instead of using conventional bedding for a softer surface and easier clean-up. The grids are kept together with standard connectors and reinforced with cable ties.
You'll need a lid for your C&C cage if you have other pets like cats. Wire shelves make excellent lids. If you don't have any potential predators in your home, your cage can have an open top.
Storage cube grids are readily available at big box stores, and sign shops usually sell corrugated plastic to consumers upon request, so you can make your own C&C cage quite cheaply. If you can't find the materials, kits and ready-made cages are available on eBay and at the Guinea Pig Zone website.
4. Other Homemade Cages
Although using cubes and Coroplast is the easiest way to build your own cage, you can get creative and use other materials. For example, my guinea pigs have a playpen made out of a child's swimming pool. They don't live in it all the time, but it would be a suitable home if I ringed it with storage grids so they couldn't jump out.
People who can't find Coroplast sometimes make a cage from grids and use a shower curtain as the bottom liner. The specifics of your cage are limited only by your imagination, as long as the design is safe for guinea pigs.