In children, symptoms may depend on age: In infants younger than 1 month of age, symptoms may include having little or no energy (lethargy), feeding poorly, grunting, or having a fever. In children, symptoms of pneumonia are often the same as in adults. Your doctor will look for signs such as cough and a breathing rate over 60 breaths a minute.
Tap water should sit for at least an hour before adding any fish to the bowl. The water must be room temperature.
Some say you can just add the Epsom Salts to the tank and do a water change when the fish has a bowel movement. Others say it should be given in a bath. If the fish is in a quarantine tank I would leave it in the salts until they work, but not for more than 24 hours.