Resurrecting green garden fish pond

[Duke Caboom]

Previous owners built a raised fish pond. We used it as a raised bed then, when the kids were old enough I painted the natural fibreglass liner with the correct paint, added water, littles, various pond weeds and creatures that came with the lilies and an filter/pump/fountain which should easily have the capacity for the size of pond. Then we added 10 small goldfish. Everything went well for about 18 months then the water went green and a heron ate several of the fish.

When I used to clean the filter it had lots of green brown sludge but this doesn't seem to be the case anymore even though it it is still pumping at the same rate as before.

Best picture I could find.


What would you do next to get the water more clear and more attractive? Pond vacuum? Chemicals? New filter? Bigger filter?

Also - how about lighting?

Thanks

[wolfracesonic]

A pond UV steriliser is what you want. It kills the algae which clumps into large enough pieces for the filter to collect it, posh word ‘flocculation’, usually fitted on the filter return pipe work.

[Duke Caboom]

Thanks, I'll look into it. There is a UV built into the pump / fountain but I wonder if it has stopped working?

[Milnsey]

Try changing the UV bulb, they usually only last a year or two