Nothing beats having a good time in the sun in your backyard pool. However, having green pool water might ruin the fun. Once your pool turns green, it means algae have dominated, and it’s time to take action immediately.

In this article, we discuss the causes of pool algae and how to eliminate them.

Algae: what are they?

Algae are regarded as belonging to the kingdom of plants. They are photosynthetic creatures that produce their food using the sun, water, and carbon dioxide. Algae might float in the water or adhere to the pool’s walls, floor, or stairs.

It is important to treat algae as soon as possible, ideally at first sight, because they can develop swiftly and reproduce. Algae in pools normally pose little threat. It might include dangerous pathogens like salmonella, parasites, or E. coli.

Poor filtration, dangerous water, irregular or low chlorine levels, and poor water circulation can all contribute to pool algae. The most prevalent types of algae are green, dark green, yellowish green, and blue-green. Slimy green algae are the main reason why pool water turns green.

Other algae include pink algae, which, like black algae, are bacteria, and yellow algae, which have a muddy yellow or brownish tint.

Possible causes behind algae

Neglected swimming pool with debris and algae

There are algae spores everywhere. They can enter your pool by the wind, the soil, or even the rain. But when they spread in your pool’s water, transform into an algae bloom, or begin to grow on your pool’s walls, those prevalent algae spores become a concern. 

Low chlorine levels, unfavorable pH balances, filthy filters, or poor pool circulation all favor algae growth. Swimwear or toys used in an algae-filled river, pond, lake, or ocean can also spread algae.

Preventing algae is far simpler than dealing with a serious existing algae problem. Because of this, it’s crucial to maintain the proper pH balance in your pool, maintain the cleanliness of your filtration system, and wash off any toys or swimsuits exposed to natural bodies of water.

Pool algae types

The most prevalent and most easily eliminated algae are green pool algae. It spreads swiftly, clouding your pool’s water and leaving green slime on the pool’s surfaces.

A more uncommon type of algae in humid regions is yellow pool algae, often brown or mustard algae. It resembles globs of pollen or sand that stick to your pool’s shadowy edges. It is also, regrettably, chlorine-resistant. Multiple rounds of cleaning your pool’s surfaces and giving extra shock to the water are required to kill mustard algae.

A bacterium, not algae, causes black pool algae. It is quite difficult to eradicate because its roots snare into solid surfaces. Black algae must be removed thoroughly over numerous cleaning sessions, or it will immediately reappear.

How to remove algae from a pool

Dirty swimming pool water

Clean the filters often

Keep an eye on the filter pressure. You must routinely clean the filter media, perhaps every couple of hours at first, until all the algae are removed to maintain the filter media’s ability to operate at peak pressure. Dead algae will block the filters if you neglect this stage. 

You should also backwash a sand filter or a DE (Diatomaceous Earth) filter. To clean a cartridge filter, it’s best to spray it.

Brush off the pool’s walls and floor

Cleaning the algae off your pool’s walls makes it easier for chlorine to penetrate the remaining algae. Additionally, it loosens pollutants so that they may be eliminated and destroyed. Brush the walls and floor of your pool with a hard pool brush on a pole. 

Pay close attention to the negative, tight spaces and corners where algae tend to grow the most. If you don’t brush the more difficult areas, your water will fog up and obscure your view. Use a pool brush with stainless steel bristles to remove algae from your pool walls if it is made of concrete or gunite. If not, we advise employing a nylon bristle pool brush.

Water testing and balancing

To check your alkalinity and pH, use test strips, a digital kit, or a liquid test kit. By balancing your water’s chemistry right away, you can be confident that your sanitizer will work well against the algae. Pool shock will be notably inhibited by high pH or low alkalinity.

Shock your pool

Your pool’s water gets a super-chlorination boost by adding shock. Additionally, the additional sanitizer will prevent algae growth. You’ll need more shock the more serious your pool algae problem is.

As a successful algae treatment, we advise employing calcium hypochlorite shock, often known as cal-hypo shock. According to the type of algae you have, double the dose specified on the container by two, three, or four to account for the size of your pool.

  • Green algae: x2 shock
  • Dark green or yellow algae: x3 shock
  • Black algae: x4 shock

Don’t forget to shock your pool at night or dusk. The majority of the chlorine will be consumed by the sun if you shock during the day before it has an opportunity to destroy the algae. 

Additionally, put your cleaning instruments in the shallow part of your pool so they may be disinfected while the shock is submerged, such as your vacuum head or pool brush.

If you circulate the shock, run your filter for eight hours or overnight. Repeat the brushing and shocking method if there is still a lot of algae in your pool.

Utilize a pool algaecide

Several effective algaecides destroy algae right away. However, they are practically all just glorified chlorine and acid solutions. Depending on the manufacturer, these algaecides may need to be applied in large quantities and might be costly. 

To stop algae from forming in your swimming pool, add 200mL each week. Also, algaecides frequently include metal bases, and you don’t want to over-metalize your swimming pool since metal in water may cause discoloration.

Pool algae prevention

A home swimming pool that has turned dark green from neglect

It will help to avoid future algae problems by adhering to these fundamental pool management guidelines.

  • Once a week, following storms or excessive use, test and balance your water.  You should change the alkalinity, pH, and chlorine levels as necessary.
  • Run your pump once a week during the busiest swimming season and shock your pool. 8–12 hours daily are needed to circulate your water completely.
  • Regularly clean or backwash your filter.
  • Before reintroducing your swimming pool’s floats, toys, and equipment, wash and sterilize everything first.
  • If you see the start of algae growth, add flocculant or algaecide immediately.

Final thoughts

The type of algae easiest to remove from your pool is green algae. It is slimy, develops on pool walls and floors, is floatable, and can cause the water to become green. It’s better to take care of it as soon as you see it since it can hold dangerous bacteria and swiftly multiply.

Also possible is mustard algae, which is more difficult to eliminate. There can also be black algae, which is the hardest to remove and is a type of bacteria rather than algae. To help you address your algae issues, feel free to use the information presented above.