At final close-down once water temperature is below 12 C and you have shocked to 10 ppm chlorine.

10 ml per m³ as a one-shot. For a 40 m³ pool that is 400 ml.

Will it work all winter?

Yes for 4-6 months under cover, longer in cold climates. Re-test at spring opening.

Will copper stain my pool?

Only if pH drifts low or copper concentration spikes; staining at correct dose and pH is rare.

Do I need pipe antifreeze too?

Yes. Algaecide protects water; antifreeze protects pipework. Both are needed for winter.

What is the active ingredient?

Chelated copper sulphate pentahydrate at 4-6% w/w available copper.

Why does it work in cold water?

Copper is a metal ion poison to algae and works by direct contact, not enzymatic process; cold does not stop it.

How is copper removed in spring?

Sequestrant binds free copper into a soluble complex that the filter removes; residual is then below 0.3 ppm.

Shock to 15 ppm; brush; vacuum dead algae to waste; resume polyquat for season prevention.

Drop pH to 7.0; brush; dose sequestrant; rebalance.

Winter algaecide vs polyquat?

Winter algaecide is copper-based for cold dormant water; polyquat is for active swim-season prevention. Use one in season, the other for closure.

Winter algaecide vs winteriser?

Algaecide stops algae in the water; winteriser is the broader chemical pack including antifreeze and shock. Use both at close-down.

Pool Winter Algaecide - Long Dwell Concentrate

Name: Pool Winter Algaecide - Long Dwell Concentrate
Brand: ClearSpa
SKU: pa-3
Availability: InStock
Rating: 5.0 (3 reviews)

Copper-based winter pool algaecide that prevents algae growth through closed pool months. One dose at close-down keeps water clear under the cover until spring.

Prevents algae growth through 4-6 months of pool closure.
Single one-shot dose at winterising.
Active even at near-freezing water temperatures.
Compatible with winterising chemicals and pipe antifreeze.
Cuts spring opening time and chlorine demand.