Algae blooms are a common occurrence in outdoor ponds. Most outdoor ponds are closed re-circulating aquatic systems which lack a fresh water flow through source. In these closed systems, nutrients and carbon dioxide will build up and create two classes of Algae; Planktonic algae and filamentous algae.
Planktonic algae are waterborne single cell algae. Planktonic algae turn the water green. This is called an Algae bloom. Sunlight and the nutrients and carbon dioxide in your pond’s water combine to create algae blooms. The nutrients come from uneaten fish food, fish waste including ammonia, and organic matter such as decomposing leaves. The more sunlight a pond receives, the better the chances of algae forming in your water.
The most effective method of Planktonic algae control is ultraviolet sterilization. Artistic Landscapes has used ultraviolet lights from many different manufacturers. We have concluded that the most effective ultraviolet lights for both performance, longevity and ease of use are Smart U.V.’s manufactured by Emperor Aquatics. These products can be seen at www.emperoraquatics.com. A more detailed description of ultraviolet lights is given below.
Planktonic algae can be controlled with aquatic plants, shade, ultraviolet sterilization or chemical methods. Using aquatic plants as an algae control requires that a specific number of
mature plants are added to the pond to compete with the algae for the available nutrients and carbon dioxide. Our experience shows that if enough sunlight reaches the pond, algae are likely even with plants. If the plants create enough shade, algae can be prevented. Shade is available only if foliage or a shelter inhibits the pond’s exposure to sunlight. Some Koi enthusiasts have constructed a shelter over their pond with a black netting to protect the water from the sun. While effective, it is not natural in appearance. Chemical treatments can be successful, but they can be expensive, temporary, and potentially harmful to plants and fish.
UV sterilization is a proven method for controlling waterborne algae. Combining sterilization with adequate mechanical filtration and operating the two properly is most effective in eliminating algae blooms and maintaining clear water. This combination will not, however, control nitrogen or carbon dioxide levels. Practical fish stocking densities and responsible feeding, along with routine filter and UV sterilizer maintenance play a big part in achieving a balanced system. Partial water changes (approximately ten percent of the pond volume weekly with non-chlorinated water) will aid in diluting nutrients.
Algae blooms can be controlled with an ecologically balanced pond. Seeding your pond with bacteria such as Microbelift is the quickest way to achieve this balance. Plants are essential to maintaining an ecologically balanced pond. Plants eat the same food as the algae (nutrients) while also absorbing the suns rays. Light and nutrients are the food of both plants and algae. Water lilies provide shade to the water while providing beautiful flowers. Water hyacinth and water lettuce also shade the water and their floating root systems absorb nutrients needed for algae. These plants reproduce rapidly. They are best suited for the biofalls surface, and can be kept in place with fishing line. Throw away older plants. The roots of these plants if placed in the pond itself are a favorite food for fish, especially Koi. In fact, Koi will eat all of these plants in the pond. Your water lettuce will soon become shredded lettuce.
Biofiltration will eat the nutrients needed for algae as well. Biofilter medium in the biofalls and gravel at the bottom of the pond are great places for bacteria to colonize. Another great place is a bog pond or veggie filter. This is a shallow section of the pond that the pond’s water circulates through, usually at the top of a waterfall. Fine meshed foam pads can also remove algae from the water. Never use lawn fertilizer or plant insecticides near your pond, as these will cause large nutrient blooms that may threaten your aquatic life.
If your pond currently is full of algae, the quickest way to clear the water is to install a U.V. light and perform a partial water change. Once the water has cleared, bacteria such as Microbelift should be added to the pond. The U.V. light needs to be turned off for 48 hours after the bacteria are added. The U.V. light will kill new bacteria. Once a good bacteria colony has been established, enough new bacteria will be produced to offset the bacteria killed by the U.V. light.
The lamps in a U.V. light burn out every six months. If used, they need to be placed AFTER the filter, because they kill the nutrients needed by bacteria, which break down waste materials in the pond. Keep your pond free of debris. Clean your skimmer net on a consistent basis, especially in the spring and fall. If your eco-balanced pond turns murky, it may be time to clean the foam pads in your filtration system.
Attached filamentous algae can be seen growing on the rocks of a waterfall or on the sides of the pond. The growth of filamentous algae results from high levels of nutrients, carbon dioxide, and the catalyst, the Sun’s energy. Methods of controlling filamentous algae include increased shade, reducing the frequency of fish feedings, practical water changes, and the use of chemicals or plecostomus (algae-eating fish) during the summer months. Ultraviolet lights are ineffective in killing filamentous algae because these algae, attached to objects in the pond, will not pass through the U.V. light. Filamentous algae may grow and will benefit the pond by consuming nutrients and carbon dioxide. Responsible fish feeding will encourage the fish to graze on the filamentous algae, which is good in their diet. Filamentous algae may also be harvested and used as a fertilizer in gardens; remove it by hand or with a long-bristle brush.
Algae Isn’t Bad, Is It?
Algae can be either beneficial or detrimental to a pond, depending on the owner’s viewpoint. Algae provide nutrients for newly hatched fry, and indirectly act as a color enhancer. As algae grow in a pond, a population of zooplankton will also develop, on which the fish feed. These natural live feeds help develop the intense coloration desired in most Koi. Unfortunately, algae blooms prevent viewing the fish, so that sick fish can go undetected for days or even weeks.
Algae influence the water quality of the pond mainly by affecting the balance among dissolved oxygen, pH, carbon dioxide, and nutrients. During photosynthesis, algae produce oxygen, remove nutrients, and take up respired carbon dioxide from both the fish and the algae itself. In heavily stocked ponds, the water becomes supersaturated with carbon dioxide. High levels of carbon dioxide can quickly depress the pH of the water to levels below seven if the operator is not careful to maintain proper alkalinity levels and adequate aeration for stripping. During active periods of photosynthesis (during daylight hours), algae can quickly strip the carbon dioxide out of the water, and pH levels can rise above nine in a matter of hours. Fish not acclimated to such sharp shifts may initially show signs of stress. At night, both algae and fish consume oxygen from and exhale carbon dioxide into the system. Algae compete with the fish for available oxygen in the water.
Experience has taught us about other filtration methods as well. Bead filtration systems, or converted sand filters used for swimming pools filter are not effective in handling the larger volumes of organic matter and waste found in a living aquatic system. Debris, living bacteria and algae can clog these filters and render them ineffective. Swimming pools use chemicals that would kill aquatic life to keep the water clear and reduce the amount of debris required for the filter to clean.
Pumps placed inside the pond become clogged with debris, losing efficiency and destroying the pump. A pump, its pipes, and an electrical cord inside the pond are unsightly.
At Artistic Landscapes, we believe that for a pond stocked with fish, an Ultraviolet Light is an essential part of the filtration system for both water clarity and waterborne pathogens. UV sterilization is a proven solution to waterborne pathogens commonly associated with aquatic re-circulating systems. UV treatment only takes place inside the UV exposure chamber and leaves no residual downstream, and therefore is harmless to the animals in the pool. UV sterilization is a proven solution to waterborne pathogens commonly associated with aquatic re-circulating systems.
Filamentous algae and pathogens attached to objects and lining of the pond will not pass through the ultraviolet light and are unaffected by this filtering method. UV sterilizers can kill waterborne pathogens. However the water flow rate must be slower to increase the exposure time between the microorganism and the UV light. The clearer the water, the greater the UV light penetration.