hi.. i'm assuming they are silver aros.. i have 3 silvers aros.. and two i've had since they were like 4 inches big.. generally keeping two silvers in the same tank is not really advisable.. esp juveniles.. they tend to fight a lot and one of them gets pushed to the bottom.. this happened with my lil silvers and i got another tank to separate them.. the usual combo is odd numbers..1, 3, 5... but you never know.. just keep an eye on them for now.. cheers with the lil guys..