No, zebra danios are not aggressive. Zebra danios are quite peaceful and friendly, so they’re often considered one of the best species to be included in a community tank.
With that said, certain conditions can make zebra danios aggressive. First, these fish live in schools that are hierarchical in nature. Occasionally, it may seem like they’re fighting each other, but it’s not dangerous, and the aggression will fade after the hierarchy has been set.
Furthermore, zebra danios can also become hostile if their needs are not met. For example, if they feel lonely, they’ll become stressed and attack other tank inhabitants. Lack of food, poor water quality, and an overcrowded tank may also lead them to become aggressive.