Green Water in Garden Pond

[imd123]

Also posting under Home & Garden by the way! Our well established 1500 gallon garden pond has always suffered from having green water. I have tried barley straw and a UV light and have plenty of plant cover and am certain the pond is not overstocked. On some sunny clear days the water does clear but doesn't last. Any idea what may clear it please? Thanks to anyone who replies.

[jules77]

Hi, had the same problem - it was OK as long as we had it covered, but my husband removed the vine over the gazebo covering the pond, and it started to go like pea soup. We had a UV light which we didnt think was working, but someone told us they have to be changed every six months - we put a new one in and the water is as clear as crystal now.

[imd123]

Thanks Jules

Yes UV does have to be replaced regular. This is definately not my problem. I have even tried a new bulb just in case.

[hammerman]

Ok....need a few more details of the pond. Size, depth, filter type and size, pump turnover (usually in litres per hour), fish stock and size of UV in Watts.

I would guess that your UV is possibly too small. A minimum of 15 watts is needed for your pond...preferably 20W.

Also, how long has the pond been set up ?....obviously all ponds need to get established and that amy not happen for 4 or 5 years.

I have a 3,000 gallon koi pond with 20 good sized koi, a big filter and 35w UV and i've never had a single day with green water in 3 years despite the pond being in full sun.

[imd123]

Thanks for your reply Hammerman

Got a few details. Pond established about 10 years and contains only goldfish and orfe. I am absolutely certain I am not overstocked but there is no way I can count the stock! Has depth of about 18 inches. Can't give dimensions as it is unusual shape but I have found my workings from when it was built and I calculated volume to be about 1300 gallons. Pump runs 24 hours a day between April and October.

Use Bioforce 9000 filter/uv unit. Uv is 11 watts. Can't recall make of pump but seems pretty powerful and my waterfall couldn't cope with any faster output. Filter is recommended for up to 2000 gallon volume and passes about 1000 galoons per hour. Have tried the UV on and off for some time but it never seems to have made a difference.

Hope you can advise me further from this.
Thanks

[EllyD]

Hi imd, I had much the same problem but solved it eventually by tackling it at the filter end. I stripped the filter down and gave it a thorough clean - the spongey bit was filthy - and just for good measure changed the uv bulb. I was advised it would take time for it all to take effect but in just a couple of days it was so clear I could see the bottom of the pond through clear clean water. Now I am worried the herons might take advantage and pinch my fish! EllyD.

[b.potter]

hi has anyone tried algae fix to cure green water in a pond. thankyou