What Size Cage is Best for My Pigs?
In reality, there is no best size for a guinea pig cage. The simple rule is: the bigger the better. However there are minimum cage-size guidelines that many guinea pig rescue organizations and guinea pig advocacy groups recommend. A quick search on the internet will reveal the following approximate de facto standards for minimum cage sizes:
Because guinea pigs are social creatures, it is recommended to keep a minimum of two guinea pigs together. For this reason, if you want your pigs to enjoy an optimal environment, you need never consider a cage under 7.5 sq. ft.
In general, commercial cages (I like to refer to them as "pet store cages") tend to be under 3 square-feet. Commercial cages much larger than this are difficult to find and are apt to be quite costly. For this reason, conscientious guinea pig owners tend to gravitate toward a popular class of do-it-yourself or kit cages commonly called C&C or Cubes and Coroplast cages.
Do I Have to Worry About the Floor?
Definitely! Wire floors or floor with grates are hard on your guinea pigs' feet. Harsh metal grids can trap toes and legs or otherwise damage your guinea pigs' delicate feet. Imagine if you had to spend your entire life walking on metal bars suspended a foot off the floor -- in your bare feet. Even worse -- imagine trying to run on that surface.
Incidentally, the same goes when choosing a multi-level cage with a ramp. The ramp surface should not be covered with metal grids. Bottom line: avoid cages that make your pet walk on metal bars or grids at all. For best pig health and safety, your cage should have a smooth plastic or metal bottom.
Does My Guinea Pig Cage Have to Be Fully Enclosed? Does it Need a Lid?
It depends on your situation. If your guinea pigs are sharing your home with "domestic predators" (most notably cats and toddlers) you will definitely need a lid. If your home is free of these types of threats, then a lid is not needed. Most guinea pig cages and pens tend to have at least 14" walls. Although guinea pigs do like to jump for fun (commonly called "popcorning"), they are not known for being great leapers and cannot leap anywhere near 14-inches high. Trust me -- you will never see a guinea pig in the NBA. (Not only can they not jump, they also play terrible defense.) In this case, not only is a lid not necessary, it is not recommended. We find that when guinea pigs are housed in a cage with no lid, it encourages more interaction with the guinea pigs. (It's not necessary to open the lid to pet them or pick them up.) A lidless cage will also take much of the hassle out of chores like feeding the guinea pigs and cleaning the cage.