As soon as temperatures drop, many people ask, “Can algae bloom in cold swimming pool water?” The simple answer to this question is yes!
As I previously mentioned in my list of pool care essentials, having a thermometer to track your pool temperature is important because algae loves to grow in hotter temperatures––generally 85 degrees or above.
Algae growth is stopped at temperatures below 40° F, but some algae can continue to survive, and like weeds in a lawn, can go dormant over the winter, coming back to life in early spring, weeks before you open the pool.
Using a pool cover is one of the simplest but most effective ways to prevent algae from growing during winter. Algae requires sunlight to bloom, and a cover will ensure the pool water remains dark throughout winter. Plus, a pool cover will also prevent other leaves, bugs and debris from getting into your pool.
One final note on algaecide: Contact algaecide is different from liquid algaecide. Many liquid algaecides don't work in cold water, and we don't recommend using them even in the warm months.
During winter, the contribution of oxygen from photosynthesis by green plants and algae is greatly reduced. This is caused by the normal fall die-off of plants and algae due to cold water. Additionally, those green plants that remain produce less oxygen because their metabolism slows in cold water.
The presence of too much algaecide can lead to a foamy pool water. Small bubbles will begin to be produced as the water is pushed through the return jet and back into the pool. Do not confuse these bubbles and foam with another common problem, which is air in your pool lines.
If you had your pool professionally winterized, and your pool has turned green throughout the winter, this may be a signal that it's time for a new cover. Pool covers can get less effective throughout years of sun exposure and general wear and tear.
You can get rid of algae quickly by vacuuming and brushing your pool, balancing your pool's water chemistry, and then shocking and filtering your pool water. Just be thorough as you clean your pool surfaces. If you leave behind even a small number of algae spores, it won't be long before they regrow and bloom again.
If your pool has been green all season you're probably super excited to close it. While it seems like the easiest option – it's not! It's much smarter to close your pool as clean as possible. Algae can grow in water as cold as 50 degrees.
Much like the veggies in your garden, when the water is cold algae won't grow. Algae is not happy if the water is below 50 degrees. The winter kit chemicals dissipate after a few weeks, but they help keep your chemicals balanced and the pool clear until your water turns into a popsicle.
Under what conditions do algae grow best? Algae grow best when they receive 10 -15 hours of sunlight a day and the temperature stays between 60-80° F.
Warmer temperatures prevent water from mixing, allowing algae to grow thicker and faster. Warmer water is easier for small organisms to move through and allows algae to float to the surface faster. Algal blooms absorb sunlight, making water even warmer and promoting more blooms.
If conditions are right, these spores can spread rapidly and take over the pool in a short amount of time. Warm weather, sunlight, lack of circulation in the water, and nitrates or carbon dioxide in the water can all be contributing factors for algae growth.
If you have a pool heater, you should turn it off. Warmth helps produce an environment in which algae can grow. You should check your pump and your pool filter. Once they are in top condition, you should run the pump until the pool is clear again.
Covering the pool is a good way to prevent algae growth. The right cover keeps algae from entering the pool, but it also keeps leaves, bugs, bacteria, and dirt from decomposing in the pool, providing algae with food.
Pool algae occurs for many reasons. Low or inconsistent chlorine levels, faulty pool filtration and poor water circulation may be to blame. Preventing pool algae from flourishing helps to keep your pool operational so you can enjoy it all season long. The key to an algae-free pool is regular maintenance.
A fiberglass pool in its worst condition can be algae-free in 24 hours. For a vinyl liner pool, the process can take 3-4 days. For a concrete pool, this can take a week or more.
Pool water turns green because of algae in the water. Algae can grow rapidly, particularly when it's warm like Summer, which is why it can surprise you overnight. This generally comes down to an imbalance or lack of chlorine in the water.
Pools can immediately turn green after shocking when they have metals like copper in the water. These metals oxidise when exposed to high levels of chlorine which makes the pool water turn green. Adding a metal control product such as Zodiac Metal Remover will help to restore the pool water.
Baking Soda and Green, Blue, or Yellow Algae
You'll need to use an algaecide to kill the algae and superchlorinate your pool to clear the water. After this treatment, test your pH and alkalinity and add baking soda to raise alkalinity to at least 100 ppm and pH to between 7.2 and 7.8.
When the levels are properly balanced, chlorine will keep the algae at bay, but the water will slowly begin to turn green as the algae take over if there's not enough. But be careful—adding too much chlorine in pool water can cause those metals to oxidize and turn the pool a different shade of green.
But is it safe to swim in a pool with algae? Whether mild or severe, it isn't recommended. Significant amounts of swimming pool algae welcome a breeding ground of harmful bacteria that feed on algae. These bacteria pose health risks to swimmers, most commonly resulting in a skin rash.
Algaecide should be added to your pool water on a weekly basis. Preventing algae is the key to fun in your pool. Algaecides act as a backup to your normal sanitization program and prevent algae from starting and growing in the pool. Algaecide should be added after every shock treatment.
The algaecide in the kit can cause some foam if there is no algae in the pool to destroy – it lingers around with nothing to kill. Spring time algaecides use surfactants to work and these molecules can react with agitation to cause froth.