Betta behavior is amazing and often spectacular to view. They are often found to be aggressive towards other bettas, thus their name betta splendens, or splendid warrior.
What people often don't know about bettas is that they are only aggressive towards other bettas but not towards other fish. That's why bettas are considered to be a good candidate for community tanks.
Despite their spectacular displays of aggression, bettas are very gentle and are commonly targeted by other aggressive fish like tiger barbs. Aggressive betta behavior can be linked to the betta's mating habits. Males do often compete for the females just like any other animals. Though certain strains of bettas are more aggressive than others, even the calmer strains still exhibit this behavior but much less often than the more aggressive strain.
Whenever one male betta spots another they begin to exhibit the well known betta behavior. They start extending their fins and opening up their gills, trying to look as big as they possibly can and appear to pose a threat in terms of their strength and ability to fight.
This behavior is called displaying or flaring. If the size difference is huge, then you can expect the smaller fish to back down. But when the bettas are just about evenly matched, they will start attacking each other, so never put two bettas together, especially in tiny fish bowls where there is nowhere to run or hide.
There are inquisitive people who discovered that bettas can't actually distinguish between an actual betta and a reflection. Using a mirror is an often entertaining way of watching a betta fight without actually injuring it, and the display could last hours or days. Even two bettas that are placed in jars would still flair at each other just as long as they can see each other. They get bored eventually though and stop their futile displays of aggression. Replacing a betta with another one would surely start another flaring match since they don't know each other and they need to establish a new pecking order.
The issue of pecking order can even be seen in a community tank. When you combine bettas in a single tank, they start showing their usual betta behavior and start fighting and biting at each other. After a while, the biggest and strongest betta emerges and becomes the ALPHA fish in the tank. As long as that fish is in the tank, there would only be minor skirmishes that would occur inside your tank. But as soon as the ALPHA fish is removed, chaos again ensues as they try to establish the pecking order.
Aggressive betta behavior can also appear in baby bettas as soon as they begin to show some fin. Flaring then starts and soon enough they would then be biting at each other's fins. That's why breeders start to place male bettas inside jars until all that's left in the tank are female bettas.
- Mischa Hill