Elevated temp and salt. Since fungus has a hard time surviving above 82F, I treat by raising temps to 84F. I use a teaspoon per gallon of uniodized sea salt (not sea mix for marine aquaria since these mixtures contain buffers). The spots are the fruiting bodies of the fungus. Most of the infection exists as fungal spores and mycelia (root bundles). So, just be sure to treat the system for 7-10 days past the day the last white spot is seen on any individual fish.
If a med is desired, I've had good results with any med containing malachite green and formaldehyde. For scaleless fish, fish fry, and eggs, I use maracyn-two