epsom salt is not the right kind of salt. Oldfishlady said aquarium salt which is basically evaporated sea water. Epsom salt is for a different problem. It is good to have on hand.
If you have non iodized salt I think you can use that. but regular table salt would probably kill him. I don't know offhand what kinds of regular eating salt would be ok. I would message Oldfishlady and ask maybe? Someone else might know what is ok too.
This is what I use, looks like it is around $2.79 for the 16oz container of it.