I have a UV Clarifier but my pond is green. What's wrong?

I have a UV Clarifier but my pond is green. What's wrong?

UV Clarifiers are an excellent piece of kit for keeping green pond water at bay.  If you already own a pond UVC, there are a few things you need to check to ensure you are getting the best from these useful pieces of equipment.
 

The UV Bulb.

It’s very common for people to be completely unaware that the UV Clarifier contains a replaceable bulb which will need changing from time to time.  The bulb will emit ultra-violet radiation which causes algae cells to die and clump together for passing through to a filter.  However, over time this radiation deteriorates so the bulb will need changing to bring this back to maximum efficiency.  As a general rule, we suggest changing the bulb once every 12 months.  For Koi stocked ponds, a more frequent change may be desirable and for ornamental ponds with no fish, a change once every 12-18 months will suffice.
 

Fish Growth.

Quite often, a filter and UV Clarifier may have been selected based on small fish just a few hardy breeds.  However, as the years pass, it’s very common for the fish to not only grow, but multiply!  Friends and family may also turn to you for rehousing the odd fish or two.  This extra biological load may mean the UVC is now under-rated for the pond and its inhabitants.  
 
As a guide, we suggest 1 watt of UV for every 1000 Litres of water in an ornamental pond (i.e. no fish), around 2 watts/1000L for small hardy fish and 4 watts/1000L for a Koi stocked pond.  So, a 10,000 Litre pond should have a minimum of 10 watts of UV assuming no fish, 20 watts for goldfish and at least 40 watts for Koi.  This should ensure the UV is sufficient for many years to come.  If in doubt, always select a UVC which is more than capable for the pond and its inhabitants, not on the cusp.
 

Pump Flow.

The Pond Pump should pass the whole pond through the UV clarifier and filter approximately once every 1-2 hours in a fish pond and ideally once every ½-1 hour in a Koi pond.  As algae cells will replicate rapidly, the UV needs the opportunity to kill these cells before they breed.  If the flow is too slow, the algae will grow quicker than the UV can kill it and things will go out of control quite rapidly.  If the old pump used to keep up but you have seen a drop in flow, give it a good clean as debris could be restraining the impeller.
 
If you need help with fault finding, algae issues or deciding on the right equipment for your pond, call Water Garden Ltd on 02392 373735 and we’ll give you friendly, expert advice.

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