Highly concentrated copper based algaecide specifically designed to control and prevent the aggressive black spot strain of algae.

Provides long lasting protection and control of black spot, as well as mustard and green algae.

Directions for use:

Key Steps:

1. Do not add chlorinated compounds or any alkaline material for at least 24 hours prior to adding Blockout
2. Adjust pH to between 7.2 – 7.6
3. Brush walls and floor of pool
4. Add product to affected areas
5. Filter pool for 2-3 hours during and after treatment
6. Clean and vacuum the pool the next morning to remove dead algae