Yes! Running too much UV through your pond can harm fish and aquatic plants. Never run your UV system for longer than recommended or use more UV than necessary, as you don’t want to remove good bacteria from the water.

Signs your pond has had too much UV include erratic fish behaviour (increased darting, hiding, loss of colour and lesions), weird temperature fluctuations, increased pest prevalence and lack of biodiversity. You may also notice your aquatic plants failing to thrive.

How to choose the correct UV size lamp for a pond? Check the flow rate, as this has the biggest impact on your ability to thoroughly remove microorganisms. As a general guide, the maximum flow rate should be 3-4x your pond’s volume.