Hi wandered if anyone could give me any advice on my pond,it's finished now and 4 months old,the trouble I'm having is the water going green,the pond is 8 feet by 4 feet and 2 feet deep,I'm using a Bermuda bio force 9000 gravity filter with built in 11 watt uv light,I didn't put the uv light on until 3 weeks ago to let the good bacteria build up in the filter,but since the uv been on its still not clearing the pond,I have a really good flow rate through my atom 3000 pump,was told to turn the flow down on the pump to let the water run slower through the uv,but this made no difference at all,I since turned it back up,I have even built a full pergola over my pond to give it some shade,the uv bulb is new and I can see it glowing,is it just the time of year when ponds will go green or do I need a bigger uv light,when I put a glass in the water it does look pretty clean but the pond looks murky,I dunno what else to do,,thanks for reading,,

Could you check on the make / model of the filter, I can not find such a filter as a "Bermuda bio force 9000 gravity filter"

Yes just checked it's the Bermuda bio uv pond filter 9000

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That's not what you first said.

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(You have to consider, I am not there, so I can only go by what you type)

But let's move on.

Your pond volume is around 1812 litres.
Your atom 3000 pump, pumps up to 3000 litres / hour

That means the whole pond volume will go through the filter around once every 30 /45 minutes.

Even if you take into consideration the pipe frictional loss and the head height loss and said the pond volume goes through once an hour its still too fast.

A good koi pond has a turn over rate of once every two hours (with bigger UV's) The average pond turnover rate should be once every 2-4 hours

Or put it this way:

You are trying to look for some one on a train from the platform, but the train is an express and does not stop.

Yes you saw the train go past but it was so quick you did not see who you were looking for.

I did read you were told to turn the flow rate down, which you did, then you turned it back up again.


A bio-filter and uv will not work for a variety of reasons, some are:
UV not on, lamp failed,old lamp, quartz sleeve covered in limescale, pipe blocked, pump not on, filter media blocked, filter too small, uv too small, flow rate too fast.


If you are sure the UV lamp is on, the only reason left is the flow rate is too high

A bio filter and uv can take anything up to 5 weeks before you get a clear pond.

Many thanks for your excellent reply and my apologies on not getting the name of the filter 100 percent right,I will turn the flow down and see how it goes I also didn't realise that a bio filter takes longer to clear the pond,thanks again for the reply ,big help

I had problems at first with my pond and the fantastic young man at Noah's ark pet shop in kidsgrove gave me a free sample of a natural algae remover that comes in sachets, I mixed it with water and left it for 12 hours for the bacteria to establish then added it to the pond, within a week it was clear after 2 applications, I'll go and ask him what it was called next time I pop in :)

hi mate..that would be great if you could get the name of it cheers