Why is my pond going green in the spring and summer.

At Joes Aquatic World we get asked by many of our customers why is our water going green even when we have a filter on the pond?

If the water in your pond is green, often likened to “green pea soup”, this is because there is suspended green algae in your water. This algae will feed off the nutrients in your water and the sun so during the spring and summer months your water will become more green.

This type of algae is so fine that a filter will not catch these fine particles and so whats the answer?

The most effective way get rid of green water in your pond is to install a Pond Ultra Violet Steralizer on to your filter system. The water will pass through these units and ultra violet light coming off the bulb in the unit will burn off the algae killing it almost instantly.

And often more importantly prevent it from returning.

There are a number of different UV Steralisers on the market such as the Evolution Aqua Evo or Kockney Koi units. They are simple to install and easy to maintain, all you have to do is to make sure that you get the right size unit for your pond.


We would suggest that you have any questions than why not contact us or give us a call we would be delighted to help.

Some customers will say I have  a UV steraliser installed either in line or in the filter box itself but still my water becomes green.

The reason for this is most likely the UV bulb has not been changed – these need to be changed every 12 months and ideally at the start of the season. A common mistake is that customers think and understandably so that if the light works then its doing its trick. This may not be the case as it is the gases in the bulb which burn the algae and they only last at full strength for approximately 6 months and then will it will begin to deterioate and after 12 month although the bulb may still light it will not be affective.

There are  a number of different bulbs depending on the wattage they will either be a Linear UV bulb (double)or compact single ended either two or four pinned



Another way of getting rid of green water in the event that you do not want to install a UV unit is use green water pond treatments there are various products available such as TAP No More Green Water or NT Labs MagiClear.

These are great treatments but they only kill the algae and do not prevent it coming back so if using these treatments you will need too continue to redose.

If there any questions you may have about treating your pond or maintaining drop us an email or contact us on 0844 3814514 and one of experts will be on hand to answer these for you.

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