are those older pictures? they don't look to large now. i have an Amarillo as well. I love him he's in a 75 g now. He's not to big and he only has had an issue with my Tetracanthus. Like most say your pair will like more space in time, but you probably have a couple of months give or take. On the same take I see many of the members who house lots of big "mean" fish together and they all live harmonious, lots of those tanks don't even have territoriality sections set up just a big ole tank with to many option to just focus aggression on one fish. best of luck