Are his gills open, too? It looks like that in the pictures, to me.
How much aquarium salt have you been adding? And for how long?
I would do a 100% water change. Do not add aquarium salt. Just use regular, conditioned water.
Do you have Epsom salt? It should be 100% magnesium sulfate. (No dyes, additives or perfumes.) If you don't have this, it's available at supermarkets and pharmacies. (But not at petstores.)
If you have Epsom salt, I would use a dosage of 0.5 teaspoons per gallon.
If you don't have Epsom salt, just do a 100% water change today, and pick up the Epsom salt tomorrow.
When doing a 100% water change, there are many ways to do this and acclimate (reintroduce) your fish back into the tank. Here is one variation:
- Note the temperature of the water.
- Using a plastic cup, scoop him, along with some of his water, into the cup.
- Clean out the tank. Refill with water at the SAME temp. Be sure to add the correct amount of water conditioner.
- Add 0.5 teaspoons of Epsom salt per gallon of water.
For example: 1 gal tank = add 0.5 teaspoons Epsom salt.
For a 2 gal tank = add 1 teaspoon Epsom salt. Etc....
- Stir until the Epsom salt is completely dissolved.
- Float his cup in the tank for about 15 min.
- Add a SMALL amount of NEW water to the cup. (Several tablespoons, or about 1.5 ounces.)
- Let his cup float for about 10 min.
- If the cup starts to fill too much, remove a SMALL amount of water from the cup. Discard it.
- Repeat steps 5-7, until an hour (or more) has passed.
- Gently release him into the tank.