What causes black spots on the surface of a new fiberglass swimming pool?

- Metal deposits: Metal minerals like iron and copper can enter the pool water from various sources, such as fill or makeup water, rain, leaves, dirt, or even household chemicals. These metals react with chlorine and other pool chemicals, forming black particles that settle on the pool surface.

- Dirt and debris: Fine dirt and debris can get into the pool from the air, wind, or people entering the pool. These particles can then react with pool chemicals or form a breeding ground for algae, leading to black spots.

- Algae: Black algae is a type of algae that can grow in swimming pools, especially if the pool water is not properly sanitized. Black algae can attach to the pool surface and form black or dark green spots.

- Fiberglass manufacturing defects: In rare cases, black spots on a new fiberglass pool can be due to manufacturing defects, such as impurities or imperfections in the fiberglass material.

Preventing black spots on a fiberglass pool:

- Maintain proper water chemistry: Ensure that the pool water has a proper pH balance, chlorine or bromine levels, and other chemical treatments to prevent the formation of metal deposits and algae growth.

- Regular cleaning and maintenance: Regularly brush and vacuum the pool to remove dirt, debris, and algae from the surface. Use a pool cover to protect the pool when it's not in use, preventing leaves, dirt, and debris from entering.

- Proper chemical application: Follow the manufacturer's recommendations for adding chemicals to the pool water. Avoid overdosing or underdosing chemicals, as this can contribute to black spot formation.

- Address metal deposits: If metal deposits are the cause of the black spots, use a metal sequestering agent to bind the metals and prevent them from reacting with other chemicals.

- Consult with a pool professional: If the black spots persist despite your efforts or you suspect a manufacturing defect, consult with a pool professional for proper diagnosis and treatment.