help with my goldfish what is wrong with him?

Have you tested the water?

Does he show any other signs of illness?

Was he in good health when you bought him?

If your goldfish is relatively new, it may be that it has common parasites that are typical in crowded community tanks (like the ones in petstores). What I would recommend is to keep an eye on the water quality, make sure all the ammonia, nitrite, and nitrate levels are within safe bounds, salt the tank with aquarium salt, and keep an eye on the fish.

With all my new fish, I usually treat for flukes with one round of Prazi Pro. It's a mild medication that won't harm the cycle, and is quite effective against common fish parasites.

you should try testing the water and checking if the water is still right.

have you seen anything else strange about it.if yes then it might have parasites or another infection.

do it's fins look rotten?