poor gupie

my little brother insisted that we buy this pretty yellow little gupie at wal-mart in the fish section to go in my fish tank. So my mom bought it for him for 4$ and when he puts it in the tank in my room it swims around, eats the fish flakes i fed it, then my oscar that iv had a year swims up and bites it in half. My brother started to cry and demanded that he get a new fish. oscarz are so pwnz!