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.
Keep your pool temperature lower
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.
That's because hot weather heats up swimming pool water where it then increases evaporation, depletes chlorine levels and messes with pH levels – all of which creates the perfect environment for algae and bacteria to grow.
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.
Warming water temperature
Toxic blue-green algae prefer warmer water. 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.
Light: Algae needs light energy to grow. The more sunlight that penetrates the area, the higher the chance for algae to sustain life. Nutrients: Nutrients, like nitrogen and phosphorus, fuel algae growth. Temperature: Warmer water leads to increased algae growth.
Algae blooms can occur when a combination of suitable environmental conditions exist for abundant algal growth (e.g., increased nutrients, warmer temperature, abundant light, and stable wind conditions).
The pH may be too high.
If the pH becomes too high (over 7.8), it prevents the chlorine from doing its job. If you're not checking the pH and it has risen too much, you could be adding the right amount of chlorine, but it can't work correctly, and algae will begin to grow.
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.
Proper chemical balance and sanitizer levels will prevent many opportunities for algae to bloom. High pH and low chlorine (or other sanitizer) can give algae a great start.
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.
A nylon or rubber brush is the correct choice for scrubbing the sides of a soft-sided above-ground pool. A large pool brush makes quick work of the job, but you may need a smaller brush to clean corners. Once the particles have been removed from the sides of the pool, turn your filter back on and agitate the water.
A late September or October closing is a great way to set up for success in the spring. If you are already suffering from an algae bloom; take care of that before you close. Opening your pool early in the spring is a good idea if you want clear water.
As soon as temperatures drop, many people ask, “Can algae bloom in cold swimming pool water?” The simple answer to this question is yes!
So while a solar cover won't actually 'turn your pool green', it will warm your water by up to 8 degrees, so if the other conditions are right, adding a solar cover can easily accelerate algae growth, very rapidly. You need to get the water balance in your pool right before putting the cover back on.
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.
Grab a brush and some baking soda. Bicarbonate, the active ingredient in baking soda, is an effective spot treatment to help kill the algae and loosen it from the wall. Make sure you really get every last particle free; black algae has particularly long and stubborn roots which makes it a persistent strand.
It's important to note that you should not try to vacuum green pool water until you have removed any and all organic debris using a pool net, and have added the proper chemicals to the water, and done proper brushing so that the green algae has visibly settled to the bottom of your swimming pool.
Too High Cyanuric Acid Level: This is probably the NUMBER ONE reason people have green pools after adding chlorine.
The most important test to take if your pool's still green after shocking is the pH level. Buy a kit or a test strip and test the pH because it will indicate whether you need to add other chemicals. A high pH means your water is alkaline and cloudy, especially after the shock.
Excess nitrogen and phosphorus cause an overgrowth of algae in a short period of time, also called algae blooms. The overgrowth of algae consumes oxygen and blocks sunlight from underwater plants. When the algae eventually dies, the oxygen in the water is consumed.
What do toxic algae look like? Toxic algae can look like foam, scum, or mats on the surface of water, said Schmale. Harmful algae blooms, which can be blue, vibrant green, brown or red, are sometimes mistaken for paint floating on the water.