Below are some reasons why some fish species are aggressive: Fighting for food. Some fish will always compete for food. An aggressive fish will fight off other fish that are perceived to be a threat ...

Most people see goldfish as harmless little pets. They swim quietly in bowls, entertain children, and seem impossible to fear ...

Just west of Toronto last summer, startled biologists counted more than 20,000 goldfish in a single urban stormwater pond the size of two basketball courts. And the fish, probably descended from ...

These amazing animals are best kept away from other less aggressive fish. From garden ponds filled with Koi Carp to the humble goldfish bowl (although goldfish really need more space to be happy and ...