Bloat can be caused by a variety of problems (diet, water quality, internal infection). What type of fish is this? What are your tank parameters? What is your tank maintenance schedule? How is your fish other than the bloat? Acting and eating normally? If he is, then it may not be an infection. If it is an infection, epsom salt may help if it's an external infection in the intestines that has moved internally causing bloat. The epsom salt will effect only the external pathogens, while you need something else to deal with the internal infection that's actually causing the bloat. I'd start with metronidazole + epsom salt. Before any treatment is initiated, you must first correct any water quality issues and clean the tank and filters to remove as much organic debris from the tank as possible.
Dosages:
Epsom salt - Start with 2 tbsp/gallon = 216 tbsp = 13.5 cups for 108 gallons. Observe the tank for at least 30 minutes after adding the epsom salt for signs of stress.
Metronidazole - Follow the directions on the package.
