If you have a new garden pond, chances are that the summer sun has turned it into a murky pot of green, algal soup. Don't panic and don't change the water. It will take a while for the pond to find its balance and clear. Shallow ponds (less than 70 cms) are more prone to algae than deeper ones. Oxygenating plants help clean the water. Covering about a third of the surface with floating plants, such as water lilies, keeps the water shaded and deprives the algae of the sunlight that they need to grow. If you have blanket weed, another type of algae, pull out as much as possible and leave it on the pond's edge to allow any trapped pond creatures to crawl back in. Tadpoles, however, tend to get hopelessly tangled in it, so remove the weed carefully on a sunny day when you can hold swathes of it up to the light for inspection. Floating pads of barley straw, which are available in some garden centres, help to stop algae growing. Lavender clippings are also supposed to help, but only in large ponds or where there is an oxygenating pump.