Betta fish are aggressive because they compete for social rank in their natural environment, which allows them to hoard food and have access to females. Although it sounds strange, this is very important for the species, since without these resources the specimens would be unable to reproduce and leave offspring. Male betta fish tend to be more aggressive. They set up territories that they defend with their lives. When another male betta is introduced into the tank, the original male will start to display warning signs. These warning signs include flaring their gills and spreading out their fins in an attempt to make themselves look like a serious threat. Are Betta Fish Aggressive? Betta fish are indeed known for their aggression. We will explore the reasons behind their aggressive nature and discuss how it is influenced by factors such as territorial instincts, breeding behavior, and environmental conditions. Are Betta Fish Aggressive Towards Humans? Betta Fish Aggressive Behavior Betta fish are very possessive creatures. These fish will attack any intruders to defend their territory. The betta fish evolved into the hostile fish you keep as pets today through years of selective breeding and domestication. While attempting to defend their food, these fish can attack other fish. The most common reasons why betta fish fight are: Territorial aggression - Male betta fish are known for being highly territorial. They will often fight other males entering their territory to protect their space. There are so many variations that betta fish are usually classified by their colors, patterns, and tail type. Their aggressive behavior is often off-putting for newcomers to the hobby. However if properly fed and cared for, you shouldn't have any problems. Bettas are generally aggressive. Males are generally more aggressive than females. It is better to keep male bettas separately. However, Male Bettas can be acclimatized to a community tank. Buy the male betta when it is young small as compared to the other fish in the tank. This ensures that it does not become aggressive. UuSC7.