High nutrient levels from fertilizer run-offs and lack of sufficient oxygen are the main causes.
As excess nutrients enter the water system, excess algae begin to grow. As the algae grow they block out sunlight which causes aquatic plants to die. The dead plants then decompose robbing the water system of oxygen and adding even more nutrients, which causes more algae and anaerobic bacterium to flourish. Now your pond looks like Pea Soup and your water is in an eutrophic state, which means water with low-dissolved oxygen and high nutrients. You can solve the problem with mechanical aerators and/or biological inoculants.
The Dangers of using Copper-based products for Pond/Lake Management
Often copper-based Algaecides are used to get rid of algae and pond scum. The advantages are that Copper is a very effective and fast algaecide, often taking just days to clear water. There are also some disadvantages that you need to be aware of, namely:
- Copper can be toxic to Aquatic life.
- Copper can cause a heavy metal build-up.
- Copper has to be frequently re-applied.
- Copper does not work with the natural system to establish ecological equilibrium.