I purchased one gallon. I only have between 1/3 acre ft. and 1/2 acre ft. So I expected to get at least 2 treatments from one gal. After applying 1/2 gal the pond water was darker but only grey. After waiting 24 hrs I had to apply the remaining 1/2 gal. to get a blacker color. Another dye I've used is blue, retails for about $32, and I can get 3 treatments from one gallon. Also, this Blue/Black Out is slower to disperse in the water than other dyes I've used. I've watched the blue dye spread through the entire pond in 2 - 3 hrs. Even with an aerator fountain running this product took at least 12 hrs to blend/disperse completely. When it is poured into the water it does not immediately begin spreading out in an increasingly wide arc. It breaks up into several individual streaks of color that do not merge quickly. It just has an odd reluctance to disperse like other dyes, and thus it's slower.