Article in English: Algae needs sunlight to grow, so if you’re still in the planning stages of a new pond, consider installing it in an area that only gets a little sun. Try building a pond near a tall wall, or use a shade mat or sail to stop algae from being able to grow.  You shouldn’t rely on shade that comes from large trees, as they may drop leaves into the pond. Fallen leaves will eventually rot and let algae grow, meaning you’ll need to clean your pond more often. Shade mats and sails are custom-made barriers that will prevent excess sunlight from getting into your pond. They should be available at specialty pond stores or online. Water that runs off from your garden may contain nutrients that algae can feed on to grow. Build a slight lip rim, roughly 1 inch (2.5 cm) high, around the edge of your pond to limit uncontrolled water from flowing into the pond. This will also help keep fertilizer, herbicides, and pesticides from getting into your pond through water runoff. All of these can be very detrimental to the health of your pond and the living things in it. There are several dyes, normally blue in color, that are designed to be added to a pond to stop sunlight from reaching the bottom, which will prevent the formation of algae. Purchase a pond dye of your choice and follow the manufacturer’s instructions to dye your pond.   Pond dye should be available online or at your local specialty pond store. The amount of pond dye needed will vary based on the size of your pond. Always follow the manufacturer’s instructions to avoid over-dyeing your pond.

Summary in Vietnamese:
Đào ao ở vị trí có bóng râm để hạn chế ánh nắng mặt trời. Xây bờ để ngăn nước mới chảy vào ao. Dùng thuốc nhuộm ao để hạn chế lượng ánh sáng mặt trời được nước hấp thụ.