POND Sources – Water Treatments – Algae – Causes and Cures

Published on January 1, 2011

1_algae_causes_and_cures_planktonic_algaeThe main reason customers are concerned about algae is aesthetics. Aesthetics is often the main reason they start a pond so as Algae accumulates leading to reduced water clarity, unpleasant appearance, oxygen deficits, and malfunction of water pumps and filters from clogging, algae is a justifiable concern. Algae is a generic term and grows in many different forms such as: “single-celled” producing green water, “filamentous” producing string algae, floating mats known as blanketweed and “macro-algae” looking like small plants. There are many different conditions for stimulating algae growth such as temperature, pH or nutrient availability.

Regardless of the type of algae growth there are two essential conditions required for growth: nutrient availability, which stimulates growth and adequate light for photosynthesis. Limiting light penetration or any single essential nutrient or will control growth. The first condition “excessive nutrients” are a growth stimulator. Experts agree that the easiest major nutrient to control is phosphate. The second condition to limit available light for photosynthesis is hard to limit in outdoor ponds. Placing dyes in the water to reduce light is acceptable to control green water, but takes away from the enjoyment many pond owners have with their fish. Additionally, water clarity is lost and often dyes will not work at all for string algae in waterfalls.

Adding higher level plants works to control algae as the plants out-compete the algae for nutrients. The key to balancing a pond based on nature is to provide enough plants and bacteria to consume the nutrients in the water. Nutrients come from using fertilizers that are not designed for water gardens, water source, ground run-off and fish waste. Many times a consumer will balance their pond for the first few years and no algae problems develop. Even when the pond size stays the same, no additional plants are added, and the number of fish remains the same, algae problems often develop. The pond owner often forgets that fish grow or multiply, plants become root bound, and sediment builds up changing the once balanced conditions they had during the first few years. When a fish goes from 4˝ to 8˝ they do not double their size, but just double in length. In reality the 4˝ fish that grows to an 8˝ fish has five or ten times more body weight. When a plant is root bound it does not grow and does not uptake nutrients properly. To rebalance the pond re-potting of plants and/or adding additional plants may be the best way to get the pond back in balance. Another problem in many ponds is the lack of partial water exchanges. Routine partial water changes reduce nutrient build-up. Reduction and removal of bottom sediment is strongly suggested to help control both nutrient loading and potential breeding grounds for pathogenic disease organisms.

When balancing a pond with plants and limiting fish to control algae, it is not always possible or feasible based on pond size or pond owner’s activities. It is important to let pond owners know alternatives are available. It is at this point that we should suggest purchasing algaecides, phosphate removers, bacterial additives, dyes and/or UV sterilizers to battle the algae problem. Each type of product has benefits and limitations.

Algaecides can be chemical or bacterial. A chemical algaecide should be one that is capable of controlling algae and is safe for use with live plants and fish. Previously, all algaecides were non-selective and killed algae, as well as killed or damaged all the plants in the pond. Some algaecides such as copper overtime becomes a problem with fish as it will accumulate in their organs shortening their lifespan. Some pond owners will shy away from chemicals for personal reasons and would prefer the bacterial approach also referred to by some as a “natural” approach. Any algaecide sold must be registered with the Environmental Protection Agency (EPA). Selling any algae control product that is not EPA registered places the retail establishment in line for a large fine. Companies that have products that are EPA registered have been provided data to the EPA to control algae, protect the environment and meet the label claims. Even EPA bacterial registered algaecides are available to control green water. The ability for bacteria to remain shelf-stable in the bottle and control algae to meet the EPA requirements has been a challenge. EPA registered bacteria work by efficient utilization of nutrients that algae needs and when used in combination with plants provide a great natural way to fight algae problems.

In water gardens we often think of algae and plants as being the primary producers and bacteria as being the major decomposers. Selected strains of bacteria are great at decomposing waste in the bottom of the pond. Other selected bacterial strains are more efficient at consuming phosphate. Some people talk about adding enzymes instead of bacteria but we need to understand that bacteria actually produce enzymes. So when bacteria are added to a pond, we are adding enzymes! Both bacteria and algae compete for the available phosphate in the pond. The key is to provide the bacteria that can outcompete the algae for phosphate. Controlling algae with bacteria is not new, but with advanced science, isolation of the correct bacteria and long-term shelf stability, EPA approved bacterial products are now available to control algae.

Whenever recommending any algae control product it is extremely important to understand that algae growth and destruction utilizes oxygen. When any pond is pea green in color or shows excess algae growth killing that algae can cause a short-term drop in oxygen, which can often result in a fish kill. Temperature of the water judges the oxygen level that can be maintained. Circulation resulting in water surface movement or splash is the best method to maintain maximum oxygen levels. When a pond owner is treating or dealing with an algae problem, advise them to run their water pumps, waterfalls or aeration devices 24 hours a day. This is a great time to sell an additional water pump or fountain for the pond.

One of the easiest nutrients to control that eliminate unwanted algae growth is phosphate. As fish waste and uneaten food decompose, phosphate is released as inorganic or reactive phosphate into the water. Reactive phosphate causes algae growth in a pond. Providing a product that precipitates out the phosphate from the water will remove the unwanted reactive phosphate. This results in less algae, crystal clear water and helps to restore and maintain the natural balance of the pond. Routine additions of a phosphate remover will help to ensure that the phosphate is out of the water.

When dealing with green water conditions the easiest and quickest way to clear the water is with a chemical based algaecide. Using a flocculating product will clear the water of the algae but often it will grow back very quickly. In some cases customers may add a flocculating product in the morning before going to work only to come home to still see the green water condition again, which results in them claiming the product did not work. When in fact the product that was added cleared the green water, but the afternoon sun caused the bloom to reappear. Another method to control green water is to add a UV sterilizer to the pond’s filter system. Remember adding a UV will only control green water and will do nothing to control string algae. It is often observed that ponds with green water that added a UV have string algae problems develop soon after the water clears. For ponds with good plant growth with green water problems the addition of an EPA registered bacterial algaecide provides superior results. The plants will utilize nutrients and the bacteria will utilize nutrients, which in combination will starve the algae of their available nutrient source. Plants and bacteria working together help to balance the pond to provide long-term clear water conditions pond owners are asking for.

The key to understanding algae problems is to understand the root cause and to find the best way to manipulate the pond to stop the algae. In many cases, the algae problem did not develop overnight and will not be solved overnight. It is essential to help pond owners understand the timeframe required to get their pond back in balance. Some pond owners will accept that their fish have grown too large and are willing to trade their now large fish in for smaller ones. Some customers become attached to their fish and even give them names. Based on the desires of your customers you should recommend the product that will best meet their needs. Whether it is a chemical based algaecide, bacterial based algaecide or even supplying them a larger pond; the goal is to help them enjoy water gardening with crystal clear water, healthy fish, and beautiful plants for their enjoyment.

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