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Types of Algae in a Water Garden
String Algae Growing on a Waterfall
String Algae Growing on a Waterfall

Types of Algae in a Water Garden

Algae in your water garden can be caused by an overabundance of fish waste and other organic material from leaves or previous algae blooms combined with excessive sunlight. Not only does all that green growth look unsightly, it ruins your water quality and creates a headache for you and your fish. Before you can make a plan for treating the different types of algae, you have to know what type you are trying to destroy.

Know Your Algae

Algae comes in two basic forms: planktonic and filamentous.

  • Planktonic algae is the floating microscopic vegetation that is the source of the pea soup type of blooms that color your pond shades of green, blue-green, brown, or variations in between. In controlled amounts, this type of algae in your water garden can beneficial as it is the start of the pond food chain. This type of tiny algae feeds fish and help to shade the pond's bottom – helping to prevent subsurface nuisance plants from growing. In uncontrolled amounts however, planktonic algae can deplete the dissolved oxygen into the pond leading to a fish kill.
  • Filamentous (string) algae is comprised of single cell plants that form long, visible chains, threads, or filaments. These threads start growing along the bottom of the pond in shallower water, on rocks, or other aquatic plants and intertwine to form mats that resemble wet wool. When these mats rise to the surface, they are commonly referred to as pond scum. These mats make great homes for micro- and macro- invertebrates, like bugs and worms, but they are also unsightly.

An Ounce of Prevention

Algae growth in a water garden is a combination of many factors, and sometimes conditions become right (or rather wrong) and different types of algae grows even in the cleanest water gardens. But there is hope. Proactively managing your pond will reduce the frequency and severity of algae blooms while providing a good ecosystem for your fish, plants, and other pond life.

  • Number of Fish and Feeding – Fish are a great addition to any pond, but over time your finned friends will grow and may even reproduce. If your pond is already at capacity, this can cause things to get a bit crowded and dirty from all the fish waste. Try to keep your fish population around 1-2 Koi or 2-3 goldfish per 200 gallons. If you have questions on your fish load, use our calculator to determine what your pond's capacity. On a similar note, feed your fish only what they can consume in a few minutes once a day and give them a quality diet. The Pond Guy Growth & Vibrance Fish Food is a high protein food, promoting growth and reducing waste left behind by your fish.
  • Aquatic Plants – Similar to algae, plants use nutrients that are in the pond. Covering 40-60% of your pond with plants not only means there will be fewer nutrients available for different types of algae to use, but they will also shade your pond – this is especially important if your pond is in direct sunlight. Just keep in mind that when the plants die back to remove them so they do not decompose and become muck.
  • Filtration – Filtering your water keeps it clean, clear, and safe for all your aquatic friends. Ponds with heavy fish loads or debris need more filtration than the average pond. If you do not think that your current filter meets the current needs of your pond, it is time to consider looking into a new unit. For tips, please see our article: I want to upgrade my filtration system. What are my options?
  • Aeration – Fish need oxygen, but a waterfall or fountain may not be enough. Using an aeration kit will infuse oxygen into the pond and are less costly to operate than pumps. Aeration will also help to make the beneficial bacteria in your pond more active so they can do their job more effectively.
  • Beneficial Bacteria – Using natural treatments will aid in keeping your pond balanced and nice. The Pond Guy Nature's Defense and Muck Defense feature beneficial bacteria that consume the excess nutrients and convert them into a harmless gas.

Have an existing algae bloom in your water garden that needs treatment? Check out our article, How to Choose an Algae Control, for tips on managing existing algae growth and different tools that are available to help you combat even the most stubborn algae.