Spring has arrived, bringing with it pleasant weather and sunlight! While most of us are relieved to see the end of the cold and rain, those who have outdoor ponds know that Spring heralds the beginning of severe algae development.
What causes algae?
Algae is basically a plant that flourishes in environments rich in nutrients, heat, and sunshine. Nutrient levels are high after winter, when ponds are often neglected. This, along with more sunlight and higher temperatures, causes algae to proliferate quickly.
How can it be prevented?
Of course, this undesirable spring bloom does not occur in every pond. So, what distinguishes those who do and those who do not? Typically, preventing algae involves eliminating the items it need to develop before it begins. One component is sunshine, which is obviously difficult to regulate. A shaded pond will undoubtedly have less algae issues, but it will not sustain light-loving (and desired) water plants like lillies. The most effective strategy to limit algae development is to remove nutrients, which may be accomplished in two ways. First, by performing a series of frequent water changes. Giving your pond a “spring clean” at the end of the winter will aid in nutrient reduction. Winter water changes are often unnecessary since fish are less active and rain water delivers fresh water to the pond. However, if you do water changes throughout the colder months, your pond will be healthier in the spring. Second, different water plants may be used to absorb all of the nutrients. A well-planted pond is also less likely to have algae issues since the water plants that have grown over the winter get a head start on the algae and can absorb the nutrients before the algae can proliferate. Filtration may also aid with algae control. Filtration does not remove the dissolved nutrients that algae feeds on, but stirring and movement of water does (algae by far prefers stagnant water). The optimum strategy is to combine all of these strategies, i.e., to have established water plants, to do occasional water changes, and to keep filtration going throughout the winter. Of course, if your pond is green now, it is too late to take these precautions, but don’t worry, all is not lost.
All of that, and my pond is still green!
It is quite difficult to get the precise equilibrium where algae does not develop. Water plants must be well established and vigorous; dead or decaying pond plants increase the nutrients accessible to algae. A pond may also take time to grow, and equilibrium is seldom attained in the first season. Furthermore, certain algae strains are more aggressive than others and will develop despite your best attempts to keep them at bay, though these are fortunately uncommon in older ponds.
A pond algicide is the greatest preventive measure if your pond is prone to algae growth. When used correctly, they are perfectly safe for fish and aquatic plants. They may also be used to keep algae at bay in ponds where water plants cannot be grown (eg smaller ponds where goldfish destroy the plants before they can grow). However, if your pond is already green, please read on before rushing out to treat it with algicide.
So how do I get rid of established algae?
Once algae has taken root, you should thoroughly clean your pond before applying algicide. Although the algicide will kill the undesired algae, the dead algae will settle to the bottom of the pond and decay, releasing new nutrients and preparing the pond for another outbreak. Rotting algae may also reduce oxygen levels, although this is more of an issue in warmer weather. If you change the water and remove the worst of the algae, not only will the algicide work more effectively, but the nutrients will be reduced and the algae will take longer to re-grow.
How do I stop it coming back?
Algicide slows the re-growth of algae, especially when nutrients are few, but it does not completely prevent it. The key is to keep up with pond upkeep throughout the warmer months. If you see algae returning, change the water and reapply the algicide before the algae may establish itself.
Spring is also a good time to start growing water plants, which will help minimise algae blooms in the coming seasons. Begin with hardy true aquatics and gradually introduce lilies and other pond plants in late spring and early summer.
Can I get fish or snails to eat algae?
Many people would prefer a more “natural” technique to reduce algae, however there are no practical solutions except from well-established plants.
Unfortunately, there are no actual algae-eating fish available for exterior ponds. The variety of fish available for outdoor use is limited since any invasive species that can live in ponds may also survive in local rivers. As a result, the importation of many appropriate species is prohibited.
Pond algae eater snails are available. The red ramshorn snail is the only species that can thrive outdoors in South Australia and all temperate zones. These little red snails consume algae, but since they are small, they cannot generally keep up with or control the excessive algae development. They are a nice addition to a pond, but they should not be expected to keep it clean. They are unlikely to have a substantial influence on an already green pond. Mystery snails may be maintained outdoors in warmer areas. Even though they are bigger and more powerful algae eaters, they will not be able to clean up an existing green pond. Furthermore, neither snails nor fish can clear algae that is floating in the water. Freshwater mussels filter floating algae but do not remove algae from pond walls. These are another beneficial addition to the pond, although they may struggle to clean a very green pond.
As previously indicated, the greatest strategy against algae is to integrate as many preventative actions as feasible. Good pond upkeep, along with the use of plants, snails, mussels, and algaecide, should result in an algae-free pond.
