Copper sulfate is the main active ingredient to some of the most popular aquatic-grade algaecides on the market. A common question we receive is whether or not our Crystal Blue products are safe to use in bodies of water that contain fish.
The general answer is yes! Being aquatic-grade products, our Copper Sulfate smart crystals and liquid Crystal Plex are formulated for use in swimming, drinking, and fishing ponds when used as directed. One exception are certain types of fish that have sensitivities to the active ingredient itself.
Fish such as koi, goldfish, trout and grass carp are extremely sensitive to copper sulfate and can be killed almost immediately if they make contact. Copper ions slow down their gill secretions and cause death by asphyxiation. Koi fish specifically are expensive, beautiful and tend to be the center point of a pond. For bodies of water with these types of fish, using algaecides containing a different active ingredient will be the key for successful treatments.