People tend to get very worked up about algae in outdoor aquatic and pond systems. The reality is all healthy aquatic systems have algae. In early season as temps rise and there is almost no aquatic top growth it tends to grow pretty fast.
In small back yard systems simple mechanical control is all you need. As top grows shades out algae and competes for available excess nutrient, the problem as you see here is largely self correcting. In the interim you get mulch, compost and or duck feed.
