Thread: Need a little help with my greenish water please.

Back last year i built myself a larger pond, ive had a pond for the last 15 years or so, the water never seemed to clear up in the new larger pond , so i swapped out my gravity fed multibay filter for a combi drum, the flow rate through the drum is 18cm3 per hour, the drum has two 40w algam UV built in and after speaking to the manufacturer they tell me i should be pumping around 15000+ per hour through it which still didnt really help?!

Now, im checking the water parameters weekly AND fitted another 55w UV aswell but still cant clear the water.
I have a build up of "hair" algae on the walls of the liner which is around 20mm long but am reluctant to use blanket answer unless necessary but am wondering if this is braking off and causing the green tinge?

I have 8 Koi, 3 grass carp and 4 smaller koi, so the pond is not over stocked as the capacity of the pond is about 15,500lts, the fish are fed once maybe twice a day, but not over fed.

The set up is :Spindrifter airated bittom drain, 4" pipework to the Combi drum (inc 2x40w Algam UV's), 20,000ltr variflow pumped back to the pond, wide mouth skimmer fed to Bakki shower with another 20,000ltr variflow pump again, unfortunately its in full sunlight, (i know shade would help)

Anyhelp on this would be great, i normally figure this sort of stuff out on my own but im a little stumped on this-Thanks

I would say you have ample uv for 15.5k lis of water, and it sounds like you’ve got a good filtration setup.
One thing that could be causing the green tinge to the water is doc (dissolved organic compounds) which can be removed by a protein skimmer, i run one on my pond and it definitely helps with the water clarity and has many other benefits also.
May be something to consider.

Originally Posted by Martin59

I would say you have ample uv for 15.5k lis of water, and it sounds like you’ve got a good filtration setup.
One thing that could be causing the green tinge to the water is doc (dissolved organic compounds) which can be removed by a protein skimmer, i run one on my pond and it definitely helps with the water clarity and has many other benefits also.
May be something to consider.

As in a Tempest or similar?

A Tempest won’t remove doc from the water. A protein skimmer is an air tight container that water is pumped through and is injected with hi volume of air causing a lot of bubbles which captures the doc from the water. I have the original Aquaforte Tornado which I’ve used for the past 17 years and still going strong.

Originally Posted by Twhitenosugar

When exactly did you put the new drum in?

The reason I ask is that your pond could still potentially be going through new pond syndrome, especially if your bio filters are new.

When I built my pond it took ages for the water to clear. It was super murky for months. To the extent that I started emailing the company I bought my Amalgam UV from saying it doesn't work. They told me to keep it on and wait.

And sure enough, eventually, once the pond matured, the water cleared up nicely.

Providing your amalgams work (obvs. Don't stare directly at them to see if they are) then I'd say keep them on 24/7 and I'd sit on your hands for a few months. The pond should clear.


Also I doubt 2cm of blanket weed on the pond walls would contribute. At most you might have a few clumps in suspension where fish have pulled some off. But it wouldn't make your water pea soup green.

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The new drum went in on April 3rd of this year, now i did think of new pond syndrome, but to try and help i put probably 80-85% of my old media in to my Bakki shower to try and help with this, but again im checking the water parrameters weekly and theyre all good.

Originally Posted by Twhitenosugar

Also I think you have more than enough UV. I have a 13,000l pond and one 40watt Amalgam keeps it clear (admittedly it is shaded by a pergola which helps).

So I suspect you maybe wasted your money on getting the extra UV, although I can appreciate why you bought it.

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Quite possibly, but i need to try something and if it turns out to be not needed i'll sell it on to some one who needs a decent UV for very little money, if only to help them out