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By Gretchen Triplett
Algae live in all ponds. It is part of the bio system that comes with ponds. The good pond algae extend over the sides and other fish pond surfaces. It grows to almost 1" in length and is a haven for microscopic life on which fish feed happily. It remains this length and is an asset to the pond. NEVER try to remove this type of pond alga. Good as this beneficial algae is, it is unable to keep the undesirable algae from forming.
Preventing algae is the best form of control. Some things to help prevent the formation of algae is to shade your pond, algae doesn't grow well in partial sunlight. Have a proper-sized pump to accommodate the size of your pond to establish a good flow of water. Keep the pond free of debris, removing all leaves before they rot. Control the pH of your water, around 7.5. Koi control string algae by eating it, but they will not help with the 'pea soup'algae. It is probably important to remember that the growth of algae doesn't affect the growth of other aquatic plants and is totally harmless to fish. Sure looks awful, though!
Algae show up most in shallow water areas. When digging your pond, keep the sides straight and one foot deep before you dig a shelf, at least. This will help.
Then, there is the not-so-good-pond alga, the suspended kind. Most of the time it is green colored, but it can be brown or red. The obvious symptom is a fish pond looking like pea soup. This algae is very tiny and even the best pond filters are usually unable to remove it. Many cures aim to rid and/or prevent this bad pond algae, such as biofilters or pond filters of any description. A biofilter may reduce the incidence, but does not prevent green pond algae forming. A simple remedy is to run the water through a thick filter such as nylon. Better water circulation also seems to help. A little shade is also suggested.
Then there is really bad pond algae - long slimy clumps - known as string algae or blanket weed or hair algae. This stuff grows at an alarmingly fast rate. It thrives in a high pH environment.
This kind of algae can make your pond look and smell horrible, and can jam up filters and pumps. It is difficult to remove and tough to control. Otherwise, the water may be crystal clear. To repeat, gardens with shallow, rock edges favor filamentous algae.
Once this kind of algae is in your pond, it is notoriously difficult to remove. Why it occurs is not well understood. But, it is important to balance the pH in the pond, which should be between 6.8 and 7.4. Kits are available for testing. Cures for algae problems abound. These include barley straw and extracts from barley straw that show promise. Some members are using barley straw.
Barley straw has been used for hundreds of years to combat algae in ponds, lakes and waterways. It produces a certain enzyme that acts like an 'organic algaecide'. It also reduces plankton (the pea soup algae).
It must be started during early spring, as soon as the ice melts, as it takes awhile for the barley straw to become active, about 3-5 weeks. Water temperatures should be 45 degrees or higher to become active. In cool weather, it may take a couple months to break down, but at warm temperatures decomposition will be effective within a month.
Apply a string to each bale and attach a rock at the other end, or put it in a bag or nylon stocking and place it where there is good water circulation. As it becomes wet and waterlogged, it will sink to the bottom of the pond. It is important to keep the straw near the surface where there is more oxygen. Attach a cork or a plastic soda bottle to the bundle to keep it afloat. After 2-3 weeks, the bale will slowly decompose and will be effective in combating algae for 3-4 months, stopping it from growing before it has a chance to get started.
In backyard garden ponds, place the barley straw bundles near the waterfall, to take advantage of the increased oxygen and the dispersion throughout the pond of anti-algae chemicals. A header pool is an ideal location for a bundle.
Technically, it is believed the barley straw releases a chemical, lignins, that inhibits the growth of algae, all the while it is breaking down and decomposing. These lignins oxidize into humic acids and other substances formed from rotting plant material. Combined with sunlight and dissolved oxygen, these substances convert to hydrogen peroxide, a proven inhibitor of algae growth. Peroxides only last a few minutes. You would need a constant flow of hydrogen peroxide into your pond water to stem the algae.
Here's where the barley straw comes in. With sufficient sunlight and oxygen, as it decomposes, the peroxides are continuously produced and the algae is continuously inhibited from growing.
Why barley straw? Well, it is not fully understood why it works better than other straw in keeping ponds algae-free. But studies have proved it works better with both string algae and blue green algae.
Barley straw only works if it is put in the pond before the algae begins to grow. It does not remove algae already present. To clear the pond, either remove the algae manually, or use some type of algaecide. Once the algae formation is under control, the barley straw will keep the algae from returning.
The amount of barley straw to use is determined by the surface area of water, not your water volume. A good rule might be to use .03 ounces of straw for every square yard of water surface, more if you've had a problem with string algae. When the alga is under control, you might not need as much. Experience will be your guide.
It is recommended to replace the barley straw after 3 months, before you remove the older barley straw before it is completely spent, as this will allow the 2-3 weeks the new barley straw requires to start decomposing.
Buy only organically grown barley straw! It will be void of harmful chemicals, pesticides, insecticides, etc and will not endanger the health or cause death of your fish or other aquatic life. Barley straw also comes in pellet form, and seems to break down faster.
Pond health definitely seems to improve with the presence of barley straw. Maybe it is because the lack of algae allows for greater penetration of sunlight and facilitates photosynthesis in the plants.
Algaecide products such as Pond Jungle, Pond Balance, Algae Fix, Aquascapes' String Algae Buster seem to work for many CIWGA members. Scoop out the string algae to start with, try one of the products, work to normalize the pH, and maybe provide some shade. Some ponds use black dye, including Longworth Gardens in Philadelphia. Reflections are magnified, while fish are camouflaged in black water.