How many fish in a 50?? :)

[George]

With so many big fish in such a tank, ammonia, oxygen, and aggression will be an issue. However those things can be dealt with easily. For ammonia problem, get yourself some prime or simiar ammonia binding thingy. For oxygen, buy a big airpump (they are cheap , less than the price for one fish). For aggression, get some egg-crate and make some tank dividers so you can separate the aggressors.
Good luck.