They are said to actually attain 5 feet, the biggest reported one is longer and heavier than the biggest reported sartc from what I know. A 240 would not do at all. And they are very territorial. Claiming all regions of the tank. The whole tank would turn into a death battle. This wouldn't work imo, you'll have a bunch of fish that are at the top in their habitat, and probably won't back down when a fight is initiated. I've no personal experience with dorado or aimara, but from even reading DB's threads they don't seem to back down from other fish if a fight is initiated. And this is if he can even find a brassy which is going to be hard. He'd probably end up with a Franky which are said to be quite a bit more aggressive. Im not sure about the average growth rates of artc because people claim different things, and who knows if they have a true artc cause those threads didn't have pictures. But mine grew rapidly to 2 feet from 14-16 inches in about 8 months. That's TL. Now that's faster than the average aimara growth rate. As for dorado idk. All the fish are out of the question regardless due to the fact that they get to large alone for the 240. As DB stated you can get some nice predatory characins that are very similar on a smaller scale size, and house them together. Pick a legal smaller species of wolf or you can try more than one species of wolf. I'd do curu and golds, maybe grow out an ery ahead of time and even try that. I like my odoe alone, can't imagine a pack being worse, only better. And then if no plants maybe add some dithers. Get some bichirs too. 4-line pims and I'd try a Asian upside down catfish because I like how they're jet black, and I'd add a leporinus. Maybe try that new similar looking species Wes has been bringing in lately, idk there's a lot you can do. Obviously maybe not house everything I said together, but those are ideas of somethings I'd do revolving around predatory characins that have worked for me in the past.Don't artc get huge, like slightly smaller, more aggressive rtcs?