Water Garden Algae Control

Green Pond?
Water Garden Algae Control-
What is the number one problem in water gardening? Algae. Whether it’s “green water” or filamentous “blanket weed,” water gardeners hate it and want it gone – now! There are so many approaches to algae control. Some say “go natural.” Others recommend chemical treatment. What works? Before you can fight algae, you have to know your enemy. Let’s take a close look at algae, and then discuss how to keep it under control.

Algae Live Everywhere
First off, algae live just about everywhere: in puddles, soil, even in your bathroom shower. It is no surprise that algae grow in water gardens. Algae require nutrients and sunlight, the same as water plants. Algae are carried into the pond by wind, rain, on the sides of fish and on plants you put into the pond. Single-celled green algae may form “pea soup” blooms, obscuring fish and submerged plants. Filamentous “blanket weed” forms floating mats at the water surface. Can algae be eliminated from the water garden? First, understand that algae are an essential part of the natural food chain in all water gardens. Algae assist in keeping the pond “in balance,” helping to maintain a healthy environment for fish and other pond creatures. Secondly, no matter how hard you try, you’ll never totally eliminate algae. We can, however, tip the scales in our favor. Follow along as I outline all that is required to keep algae problems under control.

Nature as an Example
Many water gardeners ask, “Natural ponds aren’t green. Why does mine look like pea soup?” The answer is fundamental to understanding why so many ponds have algae problems. In nature you won’t find a 500-gallon pond filled with 25 pounds of fish. Natural ecosystems cannot support this type of fish load. Compared to nature, our ponds contain several thousand times the number of fish per gallon of “living space”! Despite the notion that water gardens duplicate nature, man-made ponds are very unnatural in just about every biological and chemical aspect. This is not to say that natural processes are not contributing to the health of the pond. On the contrary, we must use and manage these processes to keep water gardens beautiful. Nowhere is this truer than in algae control. You may be thinking, “Great, now I have to be a biologist, too.” Don’t worry. I’ve outlined several steps, in order of importance, for controlling algae in water gardens. They always work……….

The Balancing Act
How many times have you heard or read that ponds must be “balanced” for healthy fish and clear water? Few, however, can explain exactly what balanced means or how it works. For our discussion on algae control, we’ll define “balanced” as: A state where algae-promoting nutrients are being removed from the water faster than they are being added. Algae get their nutrients directly from the water. When there are excess nutrients, primarily phosphate and nitrate, in the water (eutrophication), algae thrive. By limiting nutrients in the water, we reduce the amount of algae the pond can support. The result: clear water. You only have to rob algae of one nutrient to cause it to die back. Research shows that lowering phosphate and nitrate levels causes algae problems to clear up. Reduce excess nutrients as follows:

  1. Keep a reasonable amount of fish in the pond. More fish means more waste released into the water. As fish waste breaks down, it releases phosphate and nitrate.
  2. Do not overfeed the fish. The more fish eat, the more waste they create in the water. Pond fish always act hungry. Feed small amounts of food several times a day. Never allow uneaten food to remain in the pond. Use a net to skim off uneaten food after 10 minutes.
  3. Use lots of aquatic plants. Aquatic plants reduce algae growth by removing excess nutrients from the water. Floating-leafed plants like water lilies get much of their nutrients from the soil, but their leaves reduce sunlight entering the water, reducing algae growth. They have long fibrous root systems that absorb nutrients directly from the water. These plants also float, shading the water below. Growth and reproduction are so fast that water gardeners have to harvest these plants to keep them from covering the pond. Submerged plants like Hygrophyllia and Ludwigia also remove nutrients from the water. We want use as many plants as possible to keep phosphorus and nitrogen in the water as low as possible. Many water gardeners make the mistake of using too few plants. Try to cover 50% of pond surface with floating plants like water lilies and water hyacinths. Submerged plants should be planted at a rate of one bunch (6-10 plants) for every 5 square feet of surface area. Marginal or bog plants complete the balancing act.
  4. Physically remove filamentous algae from the pond. Use a net to skim off floating mats of algae as soon as they appear.
  5. Snails can eat certain types of algae.

What About Algaecides?
These work great for helping to control algae and range form chemical based products to natural ones – to see a full list of algaecides click HERE.

Do Biological Filters Remove Algae?
Biological filtration is designed to remove harmful ammonia released by fish, decomposing plants and algae, and uneaten fish food. Biological filters do not “eat” or kill algae. Pond filters will, however, trap suspended matter and help keep the water clear. A pond filter will help keep the water clear and clean. Be sure to rinse or replace filter pads and sponges regularly to keep the filters working efficiently.

The best way to control algae problems naturally is to minimize the amount of phosphate and nitrate in the water. This is achieved by properly feeding the fish and adding plenty of aquatic plants to the pond. All ponds experience an occasional algal bloom. Don’t panic -follow these tips and your pond will clear up and stay clean.