Crystal Blue, Ocean Blue, and Black Out's application rates are based on 1 surface acre with an average water depth of 4-6 feet deep.  One gallon of any of the listed colorants will treat about 1 acre 4-6 feet deep.  For our water soluble pond dye bags you would use one box for 1 acre 4-6 feet deep. 

Pond dye is largely based on personal preference.  If you want your pond a little darker add more colorant.