Plecos have a hard time surviving sometimes because cichlids, especially african cichlids, have a bad habit of trying to peck their eyes out. I've had 1 of 3 survive with my new batch of cichlids and my last batch killed 2 with none survivng. It really depends on the cichlids. My advice is to introduce fish at night and try and introduce at least 2 at a time, otherwise the cichlids tend to gang up on the new fish if you introduce only 1 at a time.