Hamster Roll Around / Zoomer Balls - Good or Bad?
From Hamster Central WIKI
1. Sight: If the ball is too dark in colour, your hamster cannot see where he is going, and will constantly run into walls, which can be very frightening to the hamster. (Many hamsters are afraid of the ball, because it's like being put into a dark box - and running into something everytime he moves!) Although coloured balls seem nicer to look at, remember your hamster already has poor eye-sight. While your hamster cannot see in the detail we human see in, they still can see CONTRAST. Putting your hamster in a clear ball is safest, and the least frightening - after running into several things in the clear ball, your hamster should figure out the contrasts of the objects/walls in your home. This cannot be achieved in a coloured ball. Note: if your hamster refuses to run in his ball (digs/scratches to get out, sits and grooms until taken out, it is possible that he's afraid of the ball.)
2. Dehydration/body temperature: If you choose to use a ball, make sure to put your hamster back in his cage for a "break" every 20 minutes or so. This will enable him to get a drink, potty, and get some cool air. (It gets hot in there!)
3. Remembering to take him out: I used to think I would never forget about my hamster in his ball - until it actually happened! Be sure to make some sort of note, set an alarm, or something of the sort while your hamster's in his ball. All it takes is for the phone to ring, or some "crisis" to cause you to forget your hamster is in it's ball.
4. Getting trapped: If you no longer hear your hamster rolling, check on him. He may be trapped behind, or under furniture/other household items. As you become more familiar with your hamster's "rolling" habits, you can block these things off.
5. Escaping: No matter how sturdy the lid seems to be, it can, and eventually will come off, allowing your hamster to escape. The cheeky furball will soon learn if he hits that particular spot a number of times off will pop the lid and wahoo... FREEDOM! A simple solution is to place a piece of tape over the lid and part of the ball after your hamster gets in it. Some balls are also liable to breaking completely in half if the hamster runs into anything, so taping around the middle of the ball is a good idea too.
6. Feet: If the air-slats are too wide your hamster's feet will get caught. You should check your hamster's feet after using the ball, to make sure his feet are not being injured. If you hear squeaking coming from inside the ball, chances are his feet are getting caught. If you have a dwarf, the mini-sized balls are best. For young and smaller Syrians, the "football-sized" are best. For super large Syrians, a "basketball-sized" is more suitable, just watch their feet the first few times. (My ZebedeeBoos uses the large "ferret" (basketball sized) ball, and so far his feet have been fine - but it may not be true for your hamster)
7. Injury/trauma: Balls can bounce down stairs, causing injury to the hamster. If you have any sort of drops in your home, make sure they are blocked off while hamster is playing. Also, do not allow anyone to "play" with the ball whilst the hamster is in it - spinning it around like a basketball can seriously injure the poor hamster stuck inside, and is not amusing!
8. Stimulation: Again, a roll-around ball can be a great toy for your hamster if used correctly/carefully... Just remember a hamster has great need to explore, and a ball will NEVER be an equal substitute to out-time. Hamster playpens are increasingly popular although these do require constant supervision.
9. Other Pets: Make sure any free-ranging pets such as cats, dogs or house rabbits are kept well out of the way (i.e. in a different room) whilst your hamster is out in his ball. The moving ball could be very tempting for these animals, whilst they may not intentionally hurt your hamster, simply playing with the ball out of curiosity could seriously injure or even kill your hamster.
Article by forum member Babyboos.