Green Water in Ponds

Green water has similar requirements to that of blanket weed. It is caused by a combination of conspiring conditions; nutrients and sunlight. Without food (nutrients) it cannot grow, without sunlight it disappears. In most ponds there are nutrients from various sources and during the summer we get at least some sun.

Regular topping up of tap water can add nutrients (depending on the quality of the tap water). Topping up with rain water can help. Also try to reduce the need to top up by reducing the amount of splashing from fountains and waterfalls.

 Nutrients can be reduced by simply reducing stocking and/or the amount you feed. There is a lot of natural food in a pond, often fish don’t need extra food provided by a human. Feeding of fish is normally only for our benefit, the fish get used to associating people with food so instead of hiding when a figure appears near the pond they think lunch is coming.

Extra planting can help to reduce green water by not only providing shade to the pond but by helping to ‘use’ up nutrients.

I tend to employ all the above methods. Chemical treatments like Tetra's AlgoRem can work but often only work for the short term.  To grantee clear water a filter system with ultra violet clarifier is required otherwise you are just relying on a natural balance which will change from month to month and year to year. If correctly sized and maintained the U.V and filter system will stop algae clouding the water.