HELP!!!! piranhas!!!!!!?

anyone that’s experienced i would greatly appreciate it. I’ve done lots of research before buying the piranhas, and the people at the pet store have bout as much knowledge as i do and only seem to follow the directions of their boss (who’s never around!!!! when i try to ask questions) and there isn’t alot of places where i live that sales or are even knowledgable about piranhas…. but i have 6 youngsters, about the size of a dime right now. I was advised that they are pigs…..but i don’t see it???? the guppies I used to cycle the tank before i bought the piranhas seem to be more pigs then the p’s are themselves???? literally the guppies eat more of their food than they do. the p’s take a few bites of the black or blood worms, or beefheart and that’s it. i dont feed them twice a day bc when i tried that….the second time (which was at night) they literally looked at the black worms crawl by and just swam away….. the water is clean i cycle 20% a week religiously, and the temp is about 80% give or take a degree or two. its not located by extreme lighting nor loud noises…. ne help would be great. i tried googling info on this but no sights seem to be helpful. thanks
i know what pacus are and NO I didnt buy pacu’s….. i also didnt buy at Petco, nor Petsmart, nor Petsupplies plus, or any other chain pet store. the petstore i purchased from is a local petstore here in sw michigan….in fact there is a big difference than pacu’s and piranhas (physically)….for one, piranhas not only have TEETH!!!!….but they have the “infamous” protruding lower jaw…..but thanks for asking any way