When it comes to swimming pools, algae can be a common problem that becomes a pool owner’s nightmare. In order to prevent or treat algae successfully, one must understand the different types and characteristics of algae to be treated.
Algae are microscopic aquatic plant-like organisms. They do not have the same structure as higher plants. There are no roots, stems or leaves. However, like other plants they require nutrients to grow and utilize sunlight to carry out photosynthesis. In swimming pools, algae can be quite a nuisance; however, they are actually the most important photosynthesizing organisms on earth. They capture more of the sun’s energy and produce more oxygen than all other plants combined. In addition, many species of animals depend on algae as a food source.
Algae vary greatly in size and they grow in many different habitats. They can endure a wide range of temperature and have been found growing everywhere from hot springs to deep within our polar ice.
Several types of algae can be found in swimming pools:
Green algae is the most common with over 7,000 different species. Green algae are bright green due to the chlorophyll (the molecule that captures light energy to carry out photosynthesis) in their cells. Green algae can be free-floating or surface-clinging and can be found in all types of pools. They are typically the easiest to treat, however, some species may be more difficult to manage than others.
Mustard algae have been described as ‘adapted green algae‘. Mustard algae also contain chlorophyll, but the green colour is masked by the presence of beta-carotene. Carotenoids (such as beta-carotene) are found in many photosynthetic organisms. These compounds are responsible for colour (like the orange colour of carrots), which is why mustard algae are yellow rather than green. Carotenoids are anti-oxidants (or reducing agents). They protect against damage caused by oxidation. Mustard algae can use these compounds as a defence mechanism to help them survive in a chlorinated environment. As carotenoids protect against oxidation, chlorine (as an oxidizer) may have little effect on algae once this defence mechanism has been activated within the cells.
Black algae are aquatic photosynthetic bacteria called cyanobacteria. They are singlecelled, but grow in large colonies. They contain chlorophyll, but they also contain compounds called phycobilins, which mask the green colour of chlorophyll. There are two types of phycobilins: phycocyanin, a blue pigment, which gives the cyanobacteria their name, and phycoerythrin, a red pigment, which exists in red or pink algae (often found around sinks and drains). Cyanobacteria are very important organisms that assist in the growth of many types of plants. They are one of very few organisms that can convert inert atmospheric nitrogen into a form that plants can use such as ammonia or nitrate.
These bacteria can grow protected from the surrounding environment. This is due to the formation of a ‘sticky layer’ on the outside of the cell. The process of photosynthesis, carried out by the bacteria, depletes carbon dioxide in the surrounding water. The decrease in carbon dioxide concentration causes the precipitation of calcium carbonate in that area. As a result, calcium carbonate, along with any other sediment that may precipitate, becomes trapped within the sticky layer. The bacteria will then grow through and over the sediment continuing to photosynthesize and develop.
This process will continue over and over again forming more layers and making the black algae difficult to treat. Brushing is extremely important when treating black algae as the protective layer must be broken in order for the sanitizer or algaecide to come in contact with the cyanobacteria.
How Algaecides Work
Quaternary ammonium compounds (quats) are positively charged and are therefore attracted to the negative charge on the cell walls of algae. This, along with the their wetting agent properties, allows quats to enter the cell wall, causing it to break. The structure of the quat makes a difference when it comes to the effectiveness of the product. Quaternary ammonium compounds have a ‘chain’ of carbons on the molecule and these carbon chains can vary in length. Through research and testing, it has been determined that biocidal activity peaks at a carbon chain length of 14.
Polymeric quat compounds work in a similar manner to ammonium chloride quats. However, because they are much larger molecules, they usually work a little slower than ammonium chloride quats.
Copper is effective at killing algae because it disrupts enzymatic activity within the cell. If the enzymes do not function properly, the organism typically cannot survive.
Ultimately, proper maintenance is the key to keeping algae growth in check. The most important consideration is the presence of sanitizer, or even better – sanitizer and algaecide. Establish a maintenance system that includes maintaining appropriate sanitizer levels, routine oxidation and application of a preventative algaecide. Remember, algae treatments will be much less effective if the pool is unable to maintain a sanitizer residual.
The physical aspect involved in pool care should also be kept in mind. Proper circulation and filtration, as well as routine cleaning and vacuuming of the pool surface are very important – particularly brushing (as mentioned previously). Once algae are exposed, the products applied for sanitization and algae prevention are able to do their job, allowing them to work more effectively.
Using products that are PMRA or EPA registered as algaecides and always following the product application directions will help ensure successful treatment and a more enjoyable pool experience for the homeowner.