Feeders are okay to feed your P's. I always quarantine my feeders for a week though. The place I get my feeders keeps them healthy and I've never had a problem yet. They also get an occassional bluegill\sunfish when I catch them. They also get quarantined.
As far as other foods, I reccommend a variety like beefheart, shrimp, pellet food, and earthworms from untreated soil. Fortunately, I live in a farming state and I can get beefheart and buffalo heart from livestock that hasn't been pumped full of steroids and other drugs. Farmers treat the cattle differently if they are planning to butcher it for themselves rather than for the market.
Don't ever feed your P's corn! I tried this once about 5 years ago and the cleanup is a mess.
Sometimes it's difficult to get heart. Allot of places just dispose of it and in the United States, the USDA doesn't like to inspect it for human consumption. I get mine from mostly small local processing lockers. It's makes the P's grow like crazy too!
Try to get it fresh\unfrozen if possible. It's easier to work with.