Giving it an appropriately large tank and aggression-free environment is more important than adding more of the kin. It is an open-water, constantly-swimming fish that needs more space than most. One of the several reasons it is called a shark is that being healthy and comfortable, it almost never stops swimming.
Dither fish of the constantly-swimming kind can help, I'd think.
Right. Their diet in the wild is mostly of plant origin, if not all when adults. They may scavenge. They can take a live prey if they have to but it is not the norm and in captivity they are one of the last fish needing live feeders.