I have had great success with tea tree oil. My nails had been affected with toenail fungus for decades and were so thickened and curled at the top that walking was painful.
I have been using tea tree oil for a few months now and my nails are already much thinner and softer, no longer curl and are pink. I use a pummice stick to gently thin the nail from time to time before applying. Be gentle, you don't want to go through the nail, just make it easy for the oil to penetrate the nail as much as possible. The dead fungus or debris turn dark so, when you file the nail too thin, the top usually, it will turn dark and brittle. Apply the oil three times a day and go barefoot as much as possible.
I agree with others here: clean socks, vinegar baths, keeping all dead skin exfoliated all help. When you add tea tree oil, it works.
My nails look and feel nearly totally normal and I know they will soon be beautiful! I'm so happy.