A swimming pool that has greenish water contains microscopic green algae. This is a common occurrence after spring or summer, when algae spores flock into the water, carried by air or rain. Many people think that unpleasant visual is the only thing green algae causes in the swimming pool, but there are various health and security risks associated with them.
When you get out of the greenish water and experience slimy sensation on your skin, it may be caused by algae that stick to your body (and swimsuit). Slimy algae layer around the pool is dangerous because it causes a slip hazard. People may hit their head on something hard, break a bone, or drown because of the slippery surface caused by algae.
Green algae also cause a headache for swimming pool guards, because the greenish tinge makes it difficult for them to spot a drowning person. Unlike what movies may tell you, a drowning person often struggles silently, without causing big splashes or commotion, and pool guards need sharp eyes to spot such person. Green algae in the water do not help.
Finally, there are health risks from bacteria that thrive in the algae colony. Illnesses such as diarrhea and Escherichia coli contamination may be caused by bacteria that live in the oxygen-rich environment among green algae. The Centers for Disease Control and Prevention even has a specific page to discuss fecal bacteria that thrive in the algae-rich pool.
Killing Green Algae with Chlorine (Shocking)
Light algae problem may only need skimming, a little sanitation, filter-cleaning, and pH-balancing to remove. However, when basic “official” methods no longer work due to stubborn algae, you can try “shocking”. This refers to a method of killing algae by exposing them to a large amount of chlorine. Here are three ways to do it:
1. Light chlorination
Light chlorination is for a pool that only has little algae, with slightly faded green color. The recommended dosage is 500 grams of chlorine for 40,000 liters of pool water.
2. Medium chlorination
Medium chlorination is used to a pool that already has darker green color, although you may still be able to see the bottom. You need around 1,500 grams of chlorine for 40,000 liters of water.
3. Extreme chlorination
Extreme chlorination is for pool with a very thick layer of green algae, resulting in dark and muddy green color. You need at least 2,000 grams of chlorine per 40,000 liters of water to remove such algae.
You must use special liquid chlorine made for cleaning a swimming pool. Make sure to do the shocking method at night, before sunlight will reduce chlorine’s performance to remove algae. Also, avoid pouring chlorine right into the skimmer.
Killing Algae Using Algaecide
Algaecide is a straightforward method to kill green algae, but it is a heavily toxic substance. Make sure you have no other options before trying this method and follow all the instructions in the package carefully. If you are unsure, call professional pool cleaner to treat your swimming pool with algaecide.
If your pool has turned dark green, regular algaecide will not work. You must use the product with at least extra 30 percent of active ingredients. You can also buy copper-based products, which can kill green algae more quickly than regular products. However, copper-based products can stain your pool after a while.
If the algae problem is light, and you do not have enough money for copper-based products, the cheap quaternary ammonia-based algaecide is enough. However, it can cause annoying foam on the surface of the water.
Finally, if you want to pour another substance, wait at least 24 hours after applying the algaecide.
Removing Algae with Floc Method
Floc method is perfect if you refuse algaecide or chlorine-related solutions. This method uses a chemical that can bind floating particles, submerging them to the bottom. Once they go down, you can vacuum and clean the pool. The steps are longer than the previous two, but the result is quite effective.
Pouring the floc requires you to turn on the recycle function in the pool’s valve. This is to help the floc chemicals circulated properly, without going through the filter. Floc is available in powder and liquid. Make sure you choose the right one, based on your budgets and pool condition. Read the labels to use it properly. Once the chemicals are poured based on directions, you can leave it overnight.
When all the particles finally come down, switch the valve to waste, and vacuum the waste particles. Add clean water to the pool by pouring it from the garden hose when you vacuum the particles. Depending on the volume of your pool, you may need to stop several times until the flying particles settle again.
What to Do after Cleaning
You can try various methods to remove green algae from the pool, even if the algae have thrived. However, the best method is to keep green algae from accumulating.
Achieve this by regulating water pH (between 7.4 and 7.6), maintaining the filter, cleaning the pool regularly, and closing it when necessary to prevent chemicals that can encourage algae growth, such as fertilizer.