Many people keep exos with piranhas, so i'd imagine conditions are the same.
For food...i'd say white fish meat, shrimp, occasional beef heart, crickets, again, much the same as piranhas - the crickets
They are great fish in a school of ten. They are much more active than Piranhas and they will eat small feeders as well. I fed mine guppies, krill, flakes, brine shrimp, and blood worms. As far as the water goes, just keep it clean and keep PH at about 7 and you should be okay. Good luck.