How can I fight algae in my pond?

Garden Experts
The water of my pond (12-15 m²) gets greener year by year. I clean my pond every year and fill in new water. I also have a couple of goldfishes in it. Previously the water was always clean. What do I do wrong or what can I do better?

The answer

Algae is a multilayer topic. But in general it´s always the same: The more nutrition there is in the water, the more algae you get. So it is necessary to keep the pond as clean as possible. For this, ideally install a powerful filter. All this is more important than algae remedies - but you can use them additionally. The mentioned fish usually have enough nutrition and need little feed. Eventually you should shorten the feed so that there is less nutrition in the water.