Algae are microscopic organisms. Common forms are single-celled green water algae and multi-cell string algae. The pea soup in your pond is the single-celled waterborne algae. The string algae usually cling to the walls of the pond and on the waterfall rocks.
A simple water change will create clear water for a day. However, the next day when the water heats up the algae will grow again and your water will become pea soup once more. Most ponds will go through an algae bloom when the pond water is changed in the spring. An algae bloom is a natural occurrence. It happens when the water heats up and there are enough decaying leaves, fish poop and other organics, known as fertilizer, in the water to create algae. Algae are at the healthiest stage when it is considered algae blooms. The free floating algae multiply so quick that your pond becomes pea soup.
In some cases, if you wait long enough your pond will clear up on its own. You could wait a month or a year. It doesn’t happen often so if you want clear water there is a list of things that you can do.
• Cleaning your pond will help since algae is fueled by the fertilizer in the pond. You can scoop debris from the bottom of the pond to help with the problem.
• Create shade for your pond. The easiest way to do this is to put plants in your pond to shade the water from the sun. Some good plants to use are water lilies, water hyacinths and other floating plants. The water will not become as warm and algae love warm water. In addition the algae will have to compete with the plants for nutrients. Hopefully the plants will win and the algae will starve and reproduce less.
• Add beneficial bacteria to the water to eliminate nutrient sources.
• Some experts suggest using “Flocculants”. It will clump the single cell algae so it falls to the bottom of the pond. The filter is then able to handle it.
• Use an ultraviolet light to sterilize the algae
The ultimate number one way to get rid of pea soup is to use the ultraviolet light. All the other things on the list will help but only the UV light will clear up the water and keep it clear. The algae in the water flow over the UV lamp. The algae become sterilized and are unable to reproduce.