1. Check the water quality: make sure that the water quality of the fish tank is clean and free of pollutants and food residues. If the water quality is not good, it may cause the fish to get sick.
2. Check the water temperature: make sure the water temperature in the fish tank is appropriate. If the water temperature is too high or too low, it may cause the fish to swim unhappy.
3. Check the health status of fish: observe whether other fish have similar conditions. If other fish don't have this situation, it may be that this fish is sick.
4. Moderate water change: Change the water in the fish tank regularly to keep the water clean, which helps to relieve the fish's illness.
5. Adjust feeding: If there are other fish in your fish tank, you should pay attention to feeding them properly to avoid food residue polluting the water quality.
If the above measures do not improve the health of fish, it is recommended to consult a professional fish therapist or aquarium staff for more professional advice and treatment.