Having a pond or water feature in your yard is a beautiful display that can bring you enjoyment and help you relax, but if unsightly algae become an issue it will detract from your enjoyment of it. Algae are plant-like living organisms that make food using sunlight.
There are three main types of algae that affect ponds in our climate- green water, algae on the surface, and string algae. Green water is a single celled alga that makes water appear green and is usually too fine to be filtered out by common pond filters. Algae on the surface look like small, green floating dots. String algae are easy to identify by the long strings, or blankets, that it produces.
For algae to grow it needs light and nutrients. It gets the nutrients it needs from dead leaves, grass clippings, fish food, fish and animal waste, dead algae and aquatic plants, fertilizer run-off, and any other organic material that may be present in your pond. The best way to prevent algae is to keep as much organic waste out of your pond as possible.
Algae on the surface and string algae can be controlled to a certain extent by hand removal. Use a fine net to skim it off the water. This will not prevent the algae from returning and this will not work for green water.
The type of filter you choose to use plays a major role in determining how clean your pond will stay. There are a wide variety of filters and pumps available on the market. They range from simple to high performance. A simple filter uses a pump to push water through the filter where algae and other debris collect. Green water cannot be controlled by a simple filter alone. A high performance filter combines the action of a simple filter with other elements such as biospheres and ultraviolet lights. Biospheres promote the growth of beneficial bacteria. The beneficial bacteria break down algae and eat the nutrients that algae would. This prevents algae from having a chance to grow. Ultraviolet lights cause algae to clump together. This makes them large enough for the filter to catch. Consult one of our water gardening experts to ensure you are using or purchasing one that is appropriate for your needs. Simple filters are usually sufficient for small water features without plants or fish. Larger ponds, especially ones that contain plants and fish, will benefit from a high performance filter.
It is important to clean your filter and your pump on a regular basis. The filter portion can be rinsed off several times before there is a need to change it. Biospheres should never be cleaned. Cleaning them will harm the beneficial bacteria that have started to grow.
There are products that you can purchase to help clear your water. Some products will turn murky water clear. Some products will cause the algae found in green water to clump together. After is has clumped together, it will be easier for the filter to catch it. If you are using a product like this it is very important to clean your filter one day after applying the product. If you do not, the algae that have been caught by the filter will break down, re-enter the pond, and cause more algae than what you started with. Another product you can buy will kill everything in your pond- algae, fish, and plants. This is generally not recommended unless you are prepared to drain your pond and restart with fresh water.
For more detailed information on how to prevent and control algae talk to one of our water gardening experts.