Bleeding heart tetras and cardinal tetras are both peaceful schooling fish that prefer to live in groups. They can become stressed and susceptible to disease if they are housed with aggressive fish. In addition, male bettas may view the tetras as competition for food and territory, leading to aggression and potential harm to the tetras.
To ensure the well-being and safety of all fish, it is best to keep male bettas in separate tanks or with compatible tankmates known to coexist peacefully.