Between 1/4 and 1/2 teaspoon per gallon added to your regular feeding. A 1/2 teaspoon per gallon will bump the ppm's by a little over 200. Weeks three through six or seven is a good range to add it. Add some epsom salts as well for extra sulfur, 1/2 -1 teaspoon per gallon. That will basically replicate most of the bloom boosters out there for pennies instead of dollars.