They are a peaceful bunch most of the time but can show signs of aggression when crowded or surrounded by aggressive tank mates. Therefore, it’s important that their tank is big enough, and that they have suitable tank mates (more on this later). Some people mistake Molly Fish breeding behaviors as signs of aggression.

Why are my mollies aggressive?

Why are my mollies fighting? The reason mollies are fighting and chasing each other around the tank is all down to mating behavior. The fighting you are seeing is males either chasing females or sparing with other males. Having the male to female ratio correct will help solve the problem.

Are mollies territorial fish?

Mollies are friendly, peaceful fish that generally get along with their tank mates well. They have been known to act territorial when around food and defending their homes, but as long as they have a large enough tank with suitable tank mates they will be just fine.