There are many cages available for hamsters but there are many factors to consider when choosing a cage for your dwarf hamster. You want to pick a cage that is a good size, escape-proof, safe, and easy to clean. Unfortunately, many cages that you will find at the pet store do not meet all these requirements when it comes to dwarf hamsters or Chinese hamsters since they are much smaller than their larger Syrian hamster cousins.
Your main choices will be between a wire cage (usually on a plastic base), a plastic modular cage (the kind with many compartments and tubes), or an aquarium (with a secure mesh lid). Each cage style has advantages and disadvantages.
Ease of Cleaning the Cage
In general, a wire cage with a plastic tray is the easiest to clean. You just lift the wire off the bottom, clean out the bedding, and wipe down the wire part and base as necessary. The more complex the cage, the more difficult it will be to clean, which is very important if you are looking at a plastic cage with multiple compartments and tubes. These cages can become a real chore to clean. Aquariums are not terribly difficult to clean but can be heavy and awkward to handle at cleaning time. Let's face it, cleaning cages is not a fun task, so keeping it easy will make owning a hamster more fun.
Ventilation in Cages
A wire cage is easily your best option when it comes to talking about ventilation and cages.
The tubes and enclosed compartments of plastic modular cages can pose real problems with ventilation so air quality and condensation can become issues. Likewise, aquariums also have inadequate ventilation. Keep in mind that the openness of wire cages gives them great ventilation but means you must also keep the cage out of drafts.
Plastic cages and aquariums do offer better protection from drafts.
Size of Cages
Despite their small size, dwarf hamsters need ample space to run and play and the actual floor space of the cage is an important factor (many modular cages seem quite large but actually have little free floor space). In general, many cages marketed for hamsters are too small. Aim for a minimum of 24 inches by 12 inches with the cage being at least 12 inches tall. However, to keep your hamster active and happy, try to get a bigger cage. When it comes to hamster cages, bigger is always better!
Cage Security and Safety
The space between the bars on a dwarf hamster cage should be no more than 1/4 inch apart - a dimension that is really difficult to find on wire cages that are large enough. Check the doors on any cage to make sure they are secure, as hamsters can become quite the experts at opening doors (on wire doors a clip can be used to "lock" doors for an extra level of security). If you choose a cage with multiple levels or tubes make sure there is no place where your hamster could fall a long distance.
Dwarf Hamster Cages and Chewing
The drive and ability of hamsters to chew can affect the type of cage they are suited for. Regarding plastic cages, make sure there are no exposed edges or ridges of plastic where a hamster can start chewing the cage otherwise your hamster is likely to escape at some point. Hamsters are usually unable to chew their way out of a wire cage (they usually can't find a way to chew the smooth plastic trays) but some hamsters become almost obsessive about chewing the bars. Aquariums are advantageous in this regard as there is usually nothing that can be chewed on them (just make sure the top is secure).
Running Wheels for Dwarf Hamsters
Hamsters should have wheels and wheels should be large enough that the hamsters don't have to arch their backs to run on the wheel. Wheels should have a solid surface and no cross bars for support so no limbs or other body parts can get caught. Run-about balls are another good option for outside of the cage.
Bedding for Dwarf Hamsters
No matter what style of cage you choose make sure you can provide a nice deep layer of bedding for burrowing. This is especially important with wire sided cages. Choose one with a nice deep tray that not only allows a thick layer of bedding but also will help to reduce the amount of bedding your hamster will push or kick out of the cage.