Taking care of a betta fish without a filter can be done successfully, but it requires more frequent water changes and close monitoring of water quality. With proper care and maintenance, bettas can live healthy and happy lives in filtered and unfiltered tanks.
Why do betta fish not require filters?
Betta fish, also known as Siamese fighting fish, have adapted to live in stagnant, low-oxygen environments. In the wild, they are found in shallow rice paddies, drainage ditches, and flood plains that have very little water flow. As a result, bettas can breathe oxygen directly from the surface of the water through their labyrinth organ. This unique adaptation allows bettas to survive in unfiltered aquariums, although filtration is still recommended for optimal water quality.
How often should you change the water?
In a filtered tank, water changes of 25-50% should be performed once a week. In an unfiltered tank, more frequent water changes will be required:
- 2.5 gallons or less: 2-3 times per week
- 5 gallons: 2 times per week
- 10 gallons: 1-2 times per week
The frequency depends on tank size, the individual betta, and how heavily the tank is stocked. Watch for signs of stress like lethargy, loss of appetite, and rapid breathing, which indicate poor water quality. Large water changes up to 100% may be needed in very small unfiltered tanks of 1 gallon or less.
Use a water conditioner
A water conditioner that removes chlorine and chloramines should be added to new water before each water change. Conditioners neutralize these harmful chemicals that are found in most tap water. Bettas are especially sensitive to poor water quality.
Monitor ammonia levels
Ammonia, nitrite, and nitrate rapidly accumulate in unfiltered tanks from fish waste and decomposing organic matter. Ammonia and nitrite, even at low levels, can burn and poison fish. Purchase an accurate aquarium water test kit and measure levels once a week:
- Ammonia: 0-0.25 ppm
- Nitrite: 0 ppm
- Nitrate: 0-20 ppm
If ammonia or nitrites are above these safe ranges, immediately change at least 50% of the water. Adding live plants can help absorb some of these waste products.
Maintain proper water temperature
Bettas thrive in water between 78-80°F. Water over 84°F can cause stress, lethargy, and increase their metabolism. A submersible preset heater with a guard is safest. Monitor the temperature daily as room temperature fluctuates. Bettas become inactive below 74°F.
Provide gentle filtration (optional)
While not mandatory, a gentle filter can be added to unfiltered betta tanks over 5 gallons. Small sponge filters with an air stone provide oxygenation without strong outflow that stresses bettas. Filter media containing activated carbon or zeolite will help absorb waste products and chemicals.
Perform partial water changes
Never change all the water at once! This destroys the nitrogen cycle and beneficial bacteria that have established in the tank. Limit water changes to 50% at most. Use a siphon to vacuum the gravel to remove solid wastes. Replace the removed water with dechlorinated, temperature matched water.
Choose appropriate tank size
Bigger is always better for aquariums. A 5-10 gallon filtered tank is ideal for bettas, but unfiltered tanks as small as 2.5 gallons can work. Anything under 2.5 gallons requires very diligent maintenance. Long, wide tanks are better than tall tanks since bettas breathe from the surface. Make sure tank hoods and lids allow air exchange.
Provide plants and decor
Live or silk plants and hiding places help reduce stress on bettas. Plastic plants can tear delicate fins. Floating plants give shade and infuse oxygen into the water. Choose smooth decor without rough edges. Wash all items well before adding to the tank to remove manufacturing chemicals.
Feed a high-quality diet
Bettas are primarily insectivores and do best on a varied carnivorous diet. Feed 2-4 small meals daily of foods like:
- Pellets
- Bloodworms
- Brine shrimp
- Mosquito larvae
- Daphnia
Avoid overfeeding and remove uneaten food to prevent waste buildup. Fasting 1-2 days per week can also help prevent swim bladder problems.
Quarantine new arrivals
Setting up a separate 5-10 gallon quarantine tank reduces the transmission of diseases to your main tank. Maintain the quarantine tank like the main tank. Observe new fish for at least 2 weeks for signs of illness before transferring.
Conclusion
Caring for a betta fish without a filter is entirely possible, but requires diligent maintenance and monitoring. Frequent partial water changes, testing water parameters, and providing proper housing helps bettas thrive in unfiltered environments. While filters are not mandatory for betta care, upgrading to a filtered, heated, 5 gallon or larger tank greatly reduces workload and stress for both fish and aquarist!