I have my 6" front in with an 10" Oscar, 6" JD, 2 large Silver Dollars, 4" Sunfish, 5" rainbow fish & 7" sun cat that stays under a log all day. I had the O first and put the front in later when I got a good deal on him. They are all in a 150g tank and get along fine. I feed them an assortment of foods, but never anything live. The O is by far the biggest and fastest grower, but he is not a bully by any means and so far so good.
I know it is not species specific, but I tried all those different species tanks in the past and I like a mix of fish now. I have quite a bit of filtration and the water is crystal clear, PH, Ammonia, etc, etc, etc, is all good. I'm not into testing that much, I just watch the fish to see if they eat and appear healthy, if so, all is good.
Best of luck
Dan