I'm not sure a Space Alien Prison could maintain a whole Series. There's been many episodes of Space Operas or movies set in prisons with Aliens, and that works fine, but, pushing the premise beyond a single episode/Movie/storyline seems like it could run out of juice, really quick.
Place the prison in a space station orbiting a dead world. The world has ruins and digs trying to unearth the secrets of the long dead civilization. The prison population is used as labor.
You have your prison gangs, human supremacists, alien gangs, etc. The pilot can show an uprising on the station and the warden deals with it by purging the air and opening the cell block to space.
The inevitable escape plot will be hatched. Some convicts will want to know what is on the world, and if it is valuable.
Think of it as the anti-Babylon 5.