An annual struggle happens nearly every year for a large portion of pond owners. The dreaded “green water” and string algae. This is most common in sun facing ponds in the hot months of July & August. Green water caused by an overgrowth of microscopic algae, called an algae bloom, which occurs when there are excess nutrients like nitrates and phosphates, along with sunlight and warm temperatures. Another way to explain this green water is that there is too much nitrogen in the water and something needs to grow. Without the proper plants, the pond provides its own solution. Algae grows because something needs to “eat” this abundance of nitrogen and bring balance to the pond.
Poor Water Filtration
The solution to removing the green in your pond’s water is proper filtration and plants. I’m a huge believer in Natural Filtration Systems, which are also called Up Flow Bogs. Natural filtration filters the water in the pond by using different size rocks in the headwaters, where the water entering your pond is, to grow beneficial bacteria and annual pond plants to use the excess nitrogen. This system does take a couple of years to fully establish itself as the plants are maturing, so a bit of patience is required. Examples of great plants for a Natural Filtration System include ornamental cattails, water iris and water celery. Great aquatic oxygenating plants include water lilies, bog bean, sweet flag (I keep mine in pots because they spread fast), water iris, hyacinth, water lettuce, arrowhead, and so much more.
Incorrectly Sized Pump
A fully planted and mature pond and Natural Filtration System is the key to great water clarity and health. However, there are other factors. When sizing a pump, a good rule of thumb is to turn the water in the pond over once every hour. For example, if the pond holds 6,000 gallons the pump should be 6,000 gph or more. In addition, if the pump is 6,000 gph or more you will need to increase the diameter of the hose from 2” to 3”.
Poorly Constructed Pond
A pond constructed too shallow will also increase the probability of green water. This is due to the pond temperature; we tend to construct ponds 3’ to 4’ deep to help keep the temps cooler. This depth will also help fish survive throughout our harsh Minnesota winters. Plants like lilies also provide shade to cool the water, providing an added benefit.
Our goal when designing and constructing a pond water feature is to mimic nature as much as possible and to use natural elements to bring the water feature into balance. We also add natural products, like barley, and beneficial bacteria to help the system. These treatments are 100% natural and safe for plants, fish, pets and people. As barley decomposes, it releases a compound that acts as an “algistat,” preventing green water and filamentous algae, and promotes healthier aquatic plants by reducing algal competition. You can also purchase liquid barley extract that is heavily concentrated and already broken down.
Mechanical Options to Prevent Green Water
There are two mechanical options to aid in the elimination of green water. The first is an aerator, which is a must for fish. In fact, I keep an aerator running yearlong in my personal pond to help oxygenate the water, keeping the water clear and my fish healthy and happy. The second mechanical option is a uv clarifier. A uv clarifier provides crystal-clear water by killing free-floating, single celled algae (the cause of “green water”) and some bacteria as water passes through, improving health for fish and plants, boosting filtration, and acting as preventative for disease outbreak.
Need some help with your algae problem? Contact us to get started with pond services for your backyard pond. We are happy to help get your pond looking great without you having to lift a finger.