Copper Sulfate granules are small blue stone crystals that are great for pond algae control. This is 100% safe to use in the water immediately around fish, pets, livestock, animals and birds, as well as humans. Do not use this in koi or trout ponds – toxicity is directly related to water softness. Do NOT treat more than ¼ – 1/3 of the surface area of the pond at one time to avoid oxygen depletion. Wait 7-10 days between treatments. You will need to re-treat throughout the season, and you want to treat when the algae is in it’s early stages. We can give you all the information you need on this product if you call the hatchery.