Perca species aren't difficult to keep. They are sensitive to low oxygen levels, so keep the tank cool (15 C/59 F) and ensure plenty of water movement. They are sociable enough when young, but can be aggressive when mature. A 50-gallon tank is way too small for them, but in a 200-gallon system, six specimens should do well.
Yes, they are predatory, but using feeder fish is deeply unwise and will only bring out the worst in them. Get them onto earthworms and river shrimps now, and ultimately, try to wean them onto fresh or wet-frozen foods that are more cost effective, safer, and easier to use.
Cheers, Neale