What causes greenwater?

In certain conditions, large quantities of microscopic algae grow in the water. They create the green water that spoils the appearance of a pond by making it impossible to see plants and fish.

It’s important not to confuse green water with the long strands of blanket weed that are also very common. Green water algae are so tiny that ordinary filters cannot trap them.


How do UVCs work?

As the pond water passes the UV lamp, the light makes the algae clump together so they are caught in the filter foam or sink to the bottom of the pond. You should see an improvement in days and achieve complete clarity in 6 to 8 weeks.

A separate UVC can be connected into the hose run between the pump and filter.

Why are Hozelock Cyprio UVCs so effective?

  • Water is slowed down as it passes the lamp to increase UV penetration
  • Quartz glass tube covering the UV lamp permits effective penetration of UV rays. Ordinary glass cuts this by 90%
  • UV lamp runs at optimum operating temperature in an enclosed chamber
  • Water is kept as close as possible to the UV lamp to maximise the UV efficiency
  • Single ended lamps last longer and have higher UV output


A revolution in the efficient elimination of green water algae.

Key Benefits Include:

  • Can be positioned in almost any position to complement your pond’s needs
  • Can by fixed to the pond wall or left free standing
  • Comes with 5 metres of cable, is easy to install and maintain and comes with a 2 year guarantee

Hozelock UV 18w for up to 6000 Litres