I think you can get away with a small Niger trigger but you have to be careful when it gets larger. I had a 5" Niger trigger with some clarkii's and it never bothered them. But you know each fish might have a little different temperment. Perc's might be a different story since they are smaller/ less aggressive. I agree that you need a bigger tank, almost double if you want to get away with your list of fish to make them comfortable.