Pond UV Clarifiers, Filters & Lights

Pond UV Clarifiers — UV Lights and Filters for Pond Water

A UV clarifier is a sealed tube containing a UV-C bulb. Water flows past the bulb, the UV light damages the DNA of suspended algae and pathogens, and the dead cells then clump together for your filter to catch. Net result: green-water algae cleared in 7–14 days, kept clear permanently.

Three things UV clarifiers do

• Kill green-water (single-cell algae): the suspended algae that turns pond water pea-soup colour
• Reduce parasite and bacteria load: partial sterilisation of fish pathogens passing through the unit
• Improve clarity: water visibility goes from 30cm to full pond depth within two weeks

What UV clarifiers do NOT do

• Kill string algae or blanketweed — these grow on rocks, the UV doesn't reach them. Use a pond algaecide for those.
• Replace mechanical or biological filtration — the UV kills algae, but the dead cells still need to be filtered out
• Work properly if the bulb is old — UV-C output drops 30%+ after 12 months even if the bulb still glows. Replace bulbs annually.

Sizing a UV unit

UV clarifiers are rated by wattage. Rough guide:

• 9–11W: ponds up to 4,000L
• 18–24W: ponds 4,000–10,000L
• 36–55W: ponds 10,000–25,000L
• 75–110W+: koi ponds 25,000L+

If you have heavy fish stocking or strong sunlight on the pond (algae fuel), upsize one tier.

Flow rate matters

Water needs to spend long enough in the UV tube to get a kill dose. Most units list a maximum flow rate — exceeding it means water passes too fast for effective sterilisation. Match your pump flow to the UV unit's rating.

Replacement bulbs

Annual bulb replacement is non-negotiable. We stock UV bulbs for all common brands — Pondmax, OASE, Aquapro, Aquascape. Order a spare bulb at the same time as the unit so you have one ready 12 months later.