Pond dyes will not shade out or control noxious aquatic floating weed species. Many pond owners also use pond dyes to improve the appearance of their pond's water. Pond dyes come in either blue or black colors. Most blue pond dyes sell for $32-$45/gallon and for black pond dyes $40-$78/gallon.
Blue pond dyes will effectively treat three acre feet of water and most black pond dyes will effectively treat six acre feet of water. Your goal is to darken the pond's water to a point that you cannot see an object that is held 24 inches under the water's surface. In most cases you will need to double the application dye rate to darken the rate to achieve this goal. Dye should be added on an as needed basis to maintain that level of sunlight shading. Pond dyes should be applied at several different shoreline locations or from one location in the center of the pond. Results normally will last for up to three months or longer assuming no rapid water exchange occurs in the pond. If you add pond dyes to muddy ponds, you should expect color variations on either the blue or black dye.
There are no water use restrictions in the use of pond dyes. Dyed water will not discolor irrigated yards or stain structures in the water. Dyed water will not stain animals or humans who swim in the water. Pond dye concentrate will stain skin, clothing, and etc. if those areas are exposed to the dye.