any frozen/refrigerated processed raw white fish meat would be fine. you can get them from supermarkets but I find that asian supermarket/grocery stores have the best price and varieties.
you can breed feeders (guppies, mollies, swordtails, convicts, etc) but they may not always get eaten especially when your piranhas get bigger. too small of a prey is not worth the energy to kill I guess. you may find that some "feeders" may become tankmate in your p tank for a good amount of time before they finally get eaten.
to quarantine feeder is to isolate it in a separate tank for a period of time just to make sure it doesn't not carry any disease or parasites. some people will treat with med as a precaution. you can also feed the feeders high quality food to increase their nutrient value before they are fed to the p's. you can gut load them before you feed them to piranhas but if they don't get eaten right away then gut loading is useless.
you can breed feeders (guppies, mollies, swordtails, convicts, etc) but they may not always get eaten especially when your piranhas get bigger. too small of a prey is not worth the energy to kill I guess. you may find that some "feeders" may become tankmate in your p tank for a good amount of time before they finally get eaten.
to quarantine feeder is to isolate it in a separate tank for a period of time just to make sure it doesn't not carry any disease or parasites. some people will treat with med as a precaution. you can also feed the feeders high quality food to increase their nutrient value before they are fed to the p's. you can gut load them before you feed them to piranhas but if they don't get eaten right away then gut loading is useless.