Green water and String Algae are two different problems.
Green water is a form of very fine algae suspended throughout the water, resulting in a green cloudy water, with low visibility. This is due to an imbalance of your water features chemistry. It doesn’t necessarily mean your pond is not healthy, be patient – plant growth in early spring helps establish the proper balance.
From our years of experience, and dealings with hundreds of green water issues, we’ve learned to follow 3 basic rules of thumb. It’s very simple, but DO NOT DEVIATE from any of the rules, even slightly.
Don’t exceed amount of fish your water feature will accommodate. Do not exceed 1 inch of fish in length per square ft. of water surface area. For example, a 5’ x 10’ pond is 50 sq. ft. If all its fish were lined up in a row, they shouldn’t total more than 50 inches in length.
We recommend at least 2 - 3 of an oxygenating type of plant such as elodea or pondweed which require planting and are hardy, which means they will come back every year. Hornwort is the most popular, it’s a simple oxygenator that does not require planting and is also a hardy plant. Tropical oxygenating plants such as cabomba are also available and have an attractive soft feathery appearance but need to be replaced every year and require planting.
Unwanted algae growth is promoted by warm temperatures and sunlight. This is why surface coverage, especially in a natural pond is so important to achieve crystal clear results. The coverage takes the sunlight away from the algae, preventing it from blooming, and in the same respect it cools the water temperature so the algae won’t grow so profusely.
Try to establish at least 60% surface coverage of your water feature by June. This may be achieved by the use of a combination of different plants. The most common is the growth of hardy water lilies which provide attractive flowers and large circular leaves which float on the surface creating an excellent coverage that will come back every year.
The most popular quick coverage type of plants are tropical floating plants which provide instant surface coverage and are usually purchased in early spring when last danger of any frost has past. Most commonly being hyacinths, water lettuce, duckweed, fairy moss, etc., all very attractive. A few marginal plants around the perimeter finalize the look by standing tall and adding character to your water feature.