Small meals more frequently is the way to go!
I was feeding my P's 1/2 a beefheart cube per Pirahna 3 times a day. I'd cut them up, drop in a 1/2, and typically one P would snatch it up quickly. I'd feed the other two, and then feed them again in about 6 hours. I've only had them for a short time, and they've already grown over an inch.
//EDIT
Depending on how big your fish is, just keep an eye on their stomachs. If they're ballooning, then cut back on their portions.
It sounds good to me, but I'm just an MFK noob at the moment, so I've got plenty to learn.