That cage looks small for so many ratties or did I miss something...?

Tanks are no option for rats no matter the size. Ventilation is poor and it is bad for their respiratory system.

Males can live together and many of them do. Some have some problems and as others mentioned neutering can help. But they should not live alone unless you have tried everything with no success and even then sometimes it is just some rats will only get along with one certain rat.