Size (L)

1 L

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
  • Concentrated formula to control the most stubborn algae
  • Long lasting – single application every 3 months
  • Year-round treatment
  • Reduces risks of algae bloom after rain
  • Great for the treatment of black, mustard and green algae
  • Suitable for use with Chlorine and salt pools
  • Suitable for all filter types
  • Won’t cloud pool water
  • Salt Pools
  • Chlorine Pools
  • All surfaces
  • Above-ground
  • In-Ground
  • Small pools
  • Swim-spas
  • Monthly
  • Quarterly
  • As needed
  • To control and prevent black algae
  • Monthly or quarterly prevention and treatment of all stubborn algae types
  • In advance of or after rain, wind or other extreme weather
  • Effective in helping prevent green pools over the winter months, an ideal winterise treatment