By Kevin Vlietstra
Recently, the author received a shareworthy email from a homeowner. “I was watching The Universe (2007) on television last night, not paying a great deal of attention, as I was doing something else at the time, when I heard the narrator say something about life beginning on Earth as bacteria that grows in pools of water. My ears perked up and I heard him mention cyanobacteria, a blue-green algae. I thought, OMG, that’s what’s growing in my swimming pool. My pool is full of creepy-crawly things. Life is forming in my swimming pool.”
This observation is correct. Cyanobacteria are photosynthetic microscopic organisms that are technically bacteria. They are often called “blue-green algae,” but they can also appear yellow, brown, purple, red, or white.1 Regardless of how they are classified, cyanobacteria turn pools from clear and inviting to ugly and repelling. At the end of the day, most people simply refer to them as “pool algae.”
Algae is introduced from a variety of sources, but most commonly, these organisms are brought into pools from rain and wind.2 As a result, almost every pool has some form of cyanobacteria growing in it. Unfortunately, high concentrations of nutrients, such as nitrogen and phosphate, can promote a population explosion and result in algal blooms, especially during warm weather.3 Not only does this visually impact the water, but its pH can also climb, as algae consumes the carbon dioxide that helps keep it under control. Pool floors may also become slippery, which can be hazardous underfoot.
Preventing algae growth
Expansive algae growth can easily be prevented in any pool. First, adding a sanitizer will help neutralize enough micro-organisms to help keep the algae count down, so there is no visual impact. Frequent vacuuming or sweeping is also important to prevent accumulation of visible algae on surfaces. In addition to adding an oxidizer (typically chlorine) daily, routinely adding another oxidizer at a higher rate will help to reduce the algae count. While a non-chlorinating oxidizing shock will not remove algae, all the other contaminants can be squelched, so the primary oxidizer can keep water safe, and algae counts down.
Chlorine is a versatile chemical that prevents and solves problems. However, with too much of a good thing, there are eventually repercussions. Since chlorine is a bleaching compound, there will naturally be some colour degradation of surfaces if too much is added, or if it is repeatedly added. Other issues may compound with repeated high-level usage, such as elevated cyanuric acid (CYA) levels when using stabilized chlorine compounds. Chlorine products without stabilizers also have their hiccups, such as excessive total dissolved solids (TDS) when using sodium hypochlorite, or exorbitant calcium when using calcium hypochlorite.
Algaecides should always be considered as the last addition to pool water to keep algae at bay. By themselves, they are unlikely to keep algae from visually creating ugly pool water, but when used as a preventative along with an oxidizer, they will help to significantly reduce the amount of oxidizer needed in order to keep water clear. Knowing all the algaecide options, for both routine maintenance and mass destruction of algae, is essential to be able to choose the right one when a particular situation emerges.
