Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
They are different, and maybe Epsom salt is OK.
Why do you want to use Epsom salt?
Raise GH? Make sure you really need magnesium. Maybe your water needs calcium or both Ca and Mg. Many GH boosters have Epsom salt as the source of Mg.
Treat for Dropsy? Put the affected fish in a hospital tank so any treatment just affects that fish.