Whether betta fish need oxygen depends on their species and living environment. Below is a comprehensive analysis:
Siamese Fighting Fish (Betta splendens)
Siamese fighting fish, such as veil-tail bettas and half-moon bettas, possess a labyrinth organ that allows them to breathe oxygen directly from the air. Therefore, additional aeration is usually not required in small fish tanks. However, if the tank is too small (e.g., less than 2.5 gallons) or water temperature is excessively high—both of which reduce dissolved oxygen levels—attention should still be paid to ventilation or moderate aeration.
Chinese Fighting Fish (Parachela oxygastroides)
Chinese fighting fish, like the three-spot gourami, also have labyrinth organs and have low demands for dissolved oxygen in water. That said, a completely oxygen-free environment may still affect their metabolism and color development. It is recommended to maintain low water flow and moderate lighting to balance dissolved oxygen levels.
Special Circumstances
High-density stocking or high-temperature environments: Even labyrinth fish may suffer from insufficient dissolved oxygen if the tank is overcrowded or water temperature exceeds 28°C (82.4°F). In such cases, supplementary aeration is necessary.
Juvenile or sick fish: These fish have increased oxygen consumption. Temporary aeration is advised to support their recovery.
Conclusion
Due to their labyrinth organ, betta fish rely less on dissolved oxygen in water. However, proper control of living conditions—such as tank size, water temperature, and stocking density—is crucial for their well-being.