Just pull some long, twiggy branches across the surface a couple of times and it'll soon reduce. If you put fish in there you can wave goodbye to much chance of newts, frogs, toads or dragonfly larvae living in it. Our pond dries up most summers and is where the clay was dug out for the bricks that made the house 500 years ago. The balance of plant life is different every year, depending on the temperature and rainfall - some years it's water forget-me-not, others flag iris, and so on. It still supports a healthy population of common and great crested newts, toads, pond skaters, great diving beetles, whirligig beetles, water fleas, water boatmen .... They arrive by themselves and their numbers also vary wildly from year to year.