- Algae bloom: Algae are microscopic plants that can grow rapidly in ponds, especially when there is an excess of nutrients, such as nitrogen and phosphorus. When algae grow in large numbers, they can form a bloom that covers the surface of the pond and blocks sunlight from reaching the plants below. This can cause the water to become dark green and murky.
- Duckweed: Duckweed is a small, free-floating plant that can also cover the surface of a pond and block sunlight. Duckweed can reproduce very quickly, and it can be difficult to control.
- Silt and sediment: Silt and sediment can also cause a pond to turn dark green. Silt is fine particles of soil that are carried into the pond by runoff. Sediment is heavier particles, such as sand and gravel, that settle to the bottom of the pond. When there is too much silt and sediment in a pond, it can make the water cloudy and dark green.
- Chemicals: Some chemicals, such as fertilizers and pesticides, can also cause a pond to turn dark green. These chemicals can alter the pH of the water, which can make it more conducive to algae growth.
If your pond has turned dark green, there are a few things you can do to address the problem.
- Reduce the amount of nutrients in the pond: You can do this by reducing the amount of fertilizer you use on your lawn and by keeping leaves and other organic matter out of the pond.
- Control the algae growth: You can control algae growth by using an algaecide or by introducing plants that compete with algae for nutrients.
- Remove the duckweed: If duckweed is the cause of the problem, you can remove it by hand or by using a rake or net.
- Dredge the pond: If there is too much silt and sediment in the pond, you may need to dredge it. This can be a time-consuming and expensive process, but it is the most effective way to remove silt and sediment from a pond.