This is exactly what you need to do for now then sort it out later once you observe who is boss vs. weaklings. Ironically the new guy has a biit of good advice here while Ehh seems to like giving bad advice on a regular basis at this point, so don't take his advice and give a single Vieja a 240g tank. That's the LAST thing you need is one fish that already has an attitude becoming SUPER-dominant in a tank big enough for at least half-a-dozen fish if not more. You put him in there by himself now and you'll NEVER get him to allow anything else in there and your $2,000 tank will stay that way as long as he is in there. The key for doing this type of stuff is having enough brutes to make sure none of them receive too much focus from any of the others - without enough fish all of their attention will be on each other constantly. In any of my growouts, I always had problems in the early stages because I simply didn't have enough fish to prevent total dictatorship......slowly as I added more and more fish it started to calm down until harmony was achieved.You need to 'overstock' in order to mess up any hierarchy structure.
Add as many fish as you can at the same time to avoid any bullying.
Amazing size tank you have there! Enjoy it, don't stress!
You see, the "problem" with planning for life is exactly the issue you're having right now - you want to do right by the fish and give it ample space and a good life, but in the process of getting there they get spoiled - when in reality, just like our kids, they need to be taught to share. Funny as it sounds, a 240g could house 20 fish to start, ultimately yielding 10 that will get along peacefully, BUT they need to be raised that way or at least have other fish of equal size and power to keep them in check. This is why the use of growouts can be so handy......having them spend all that time in closer quarters teaches them to get along and when there is dissent among the ranks, we add caves, PVC pipes, and other hide-space to break up the visual barriers and let them "go to their room" when they can't play nice.
For starters, I would vote a 240g that you are trying to house multiple fish in should have a minimum of 500lbs of rock-work, a base of at least 10 PVC Pipe T-joints and various flowerpots and strawberry planters to begin. You are ALWAYS going to have problems keeping 2 Cichlids or even 3 or 4 in a tank that size.....they simply can't help themselves to causing mischief and by adding some more fish, providing 2-3 caves and hide-spots per fish and making sure these hide-spots will allow fish to completely leave the sight of others when they need to will be the best start for keeping an aggressive cichlid community.
Always remember:
Wide open tank with a few cichlids = chaos and fighting
Heavily "decorated" tank w/ more caves and hide-spaces = a good chance at success.
Simply weed out the problem fish as you observe and relocate as needed. If you're like me, you have dozens of empty tanks lying around the house