Aqueminianswered grow question 4 years ago I like to use 1 tsp of Epsom salt per 3 gallons of water. Should bring color back or fix any deficiency anywhere from 3-10 days. Only do this maybe 1 time a month, do not over feed or give to big a dose. A little Epsom salt will go a very long way. 1 tsp of Epsom in 3 gallons = 50 ppm when I mix it.