1 month old

Question
today i bought 4 hamsters at a flea market. they are about 1 month old. They seem to get along with each other. But in the past, i have had nice hamsters and the seem to get vicious and mean. They would bite as i would change the water! How can i keep my new hamsters from getting like that?

Answer
I honestly would not recommend housing multiple hamsters in an enclosure, first you would face the problem of gender.  Hamster reach sexual maturity early in life and only have a gestation period of 28 days, so you would be overrun in hamsters in less than 40 days.  Second you would face the problem of the hamsters establishing dominance in either alpha male or female.  Hamsters will fight if the home provided is not large enough this is why they try and establish dominance, so they can decide who gets more food than others AND this process will also surely lead to the death of one or more hamsters.  Just because the hamsters that are sold in pet shops are housed together does not make it a safe practice, these places expect their "product" to leave in a reasonably fast time.

In order to tame a hamster you will have to spend at least 5-10 minutes per hamster in handling but you must allow a grace period (not handling hamsters) of at least 24hrs before handling (just so the hamster feels secure in his new home), the taming time varies slightly depending on the breed of hamster.  The larger species hamsters are usually easier to tame, the females are also naturally more finicky than the males of all breeds.  Also dwarf species are also naturally more jumpy and slightly more protective of their territory.

Also a last remark, housing multiple hamsters also raises the possibility to be "vicious and mean", anyone would get vicious and mean if they were housed with other hamsters that were bullying them.