The red swordfish has a layer of frost on its dorsal fin and a large piece of tail is missing. It seems that it was bitten by other fish. It's just been back less than a week. . What to do.
In this case, the wound of your red arrow is infected by germs. First, you raise the water temperature to 3 degrees. Second, buy some Japanese yellow powder or gentamicin, and sprinkle some salt if you really don't have it. Your fish will be healthy in a week. Adjust the temperature back to 26 degrees when you are healthy. Change a quarter of water every week.