1. Water Quality: Check the water quality in the cage. Ensure the water is clean, clear, and free of any debris or contaminants. Test the water parameters, including pH, ammonia, nitrite, and nitrate levels, and make sure they are within the ideal range for your fish species. If the water quality is poor, perform a partial water change and clean the cage.
2. Temperature: Ensure the water temperature in the cage is appropriate for your fish species. Different fish species have different temperature requirements, so check the recommended temperature range for your fish and adjust the heater or water conditioner accordingly.
3. Stress: Stress can cause fish to become inactive and sit at the bottom of the tank. Stressors can include overcrowding, incompatible tank mates, changes in water conditions, or a lack of hiding spots. Try to minimize stress by providing a suitable environment for your fish, including enough space, compatible tank mates, and hiding places.
4. Illness or Injury: Fish can become ill or injured for various reasons, leading to lethargy and sitting at the bottom of the cage. Look for any signs of illness or injury, such as changes in coloration, behavior, or physical appearance. If you suspect your fish is ill or injured, consult with a veterinarian or an expert in fish health.
5. Lack of Oxygen: Ensure there is enough oxygen in the water for your fish. Check the filter and air pump and ensure they are working correctly. You might need to increase water circulation or add an airstone to provide more oxygen.
If you have checked all these factors and your fish is still sitting at the bottom of the cage, it is advisable to consult a veterinarian or a fish health expert for proper diagnosis and treatment.