Content

• To step
• Method 1 of 3: Kill green algae with chlorine
• Method 2 of 3: Other ways to control algae
• Method 3 of 3: Prevent algae
• Tips
• Warnings

Green water from floating algae is a common problem in swimming pools. Treatment often requires different chemicals and several days of waiting, especially if the algae have been allowed to accumulate for a longer period of time. Fortunately, it takes a lot less effort to prevent recurring algae if you properly maintain your pool.

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Method 1 of 3: Kill green algae with chlorine

1. Use chlorine bleach to kill algae. If your pool water is green or visibly contains algae, there is not enough chlorine in the water. The most effective way to kill existing algae and clean your pool is to shock the water with a high dose of chlorine. This usually works within 1-3 days, but can also take a week if the pool is very dirty.
   • The other methods mentioned work faster, but they do not address the underlying sanitary problems. They are also more expensive and can have unwanted side effects.
2. Brush the walls and floor of the pool. Brush vigorously to remove as much algae as possible. You can then kill and dissolve the algae bloom faster. Pay particular attention to the steps, the wall behind the stairs, and other nooks and crannies where algae like to collect.
   • Make sure the brush matches your pool. Steel brushes work well on concrete, while a nylon brush is better for a vinyl pool.
3. Pay attention to the safety of pool chemicals. You will have to work with dangerous chemicals with this method. Always read the safety instructions on the labels. In any case, follow these safety instructions when working with pool chemicals:
   • Wear gloves, goggles, and clothing that covers your skin. Wash your hands after use and inspect your clothes for spills.
   • Do not inhale the chemical fumes. Be especially careful when the wind is blowing hard.
   • Always add chemicals to the water, not water to the chemicals. Do not throw wet scoops back into the container.
   • Keep the chemicals in closed, fireproof containers, out of the reach of children, at the same height (not on shelves one above the other). Many pool chemicals can explode if they come into contact with other chemicals.
4. Adjust the pH of the pool. Use a pH test to measure the pH of the water. If the pH is above 7.6 - which is usually the case if you have algae - add a pH-lowering agent (such as sodium bisulfate), following the label instructions. Try to get a pH of 7.2 to 7.6 so that the chlorine works better and is less likely to grow algae in it. Wait a few hours and then test the water again.
   • Test sets with tablets or pipettes are more accurate than those with paper strips.
   • If the pH is back to normal, but the TA is above 120 ppm, check the label of the product you lowered the pH with to learn how to lower the alkalinity to between 80 and 120 ppm .
5. Choose an agent with chlorine to shock the water. The chlorine you normally use for your pool is probably not the best choice for shock treatment. Instead, use a liquid chlorine product especially for swimming pools. The product must contain sodium hypochlorite, lime chlorine or lithium hypochlorite.
   • Do not use lime chlorine if you have hard water.
   • All hypochlorites are highly flammable and can explode. Lithium is relatively safe, but the most expensive.
   • Do not take chlorine granules or tablets (such as dichlor or trichlor), because they contain stabilizers that you should not put in a swimming pool in large quantities.
6. Add an extra large dose for shock treatment. Check the chlorine product label to find out how to shock treatment. To combat algae, use twice as much chlorine as with normal shock treatment. Use three times the amount if the water is very cloudy, or even four times the amount if you can no longer see the top step of the swim ladder. Run the pool filter and add the agent to the water surface. (If your pool has vinyl walls, pour the compound into a bucket of pool water first to prevent discoloration.)
   • Warning - Liquid chlorine can explode and produce a corrosive gas if it comes into contact with chlorine tablets or granules. Never pour the liquid chlorine into your skimmer or other objects containing these granules or tablets.
   • Because UV rays break down chlorine, it is best to do a shock treatment in the evening and let it work all night.
7. Test the water again the next day. After the pool filter has been running for 12-24 hours, check your pool. Dead algae will turn white or gray, and will float in the water or lie on the bottom. Retest the chlorine level and pH of your water whether the algae are dead or not.
   • If the chlorine level is higher (2-5 ppm) but you still see algae, keep these values ​​the same for the next few days.
   • If the chlorine level is higher, but still below 2 ppm, shock again the following evening.
   • If there is no significant difference in your chlorine levels, your pool probably contains too much cyanuric acid (more than 50 ppm). This is due to the use of chlorine tablets or granules, which means that the chlorine is not released properly. The only way to fix this is by repeatedly shock treatment (sometimes very often) or by partially draining your pool.
   • Large amounts of dead leaves or other debris can also lower chlorine levels. If the pool has not been used for a while, it can take up to a week and several shock treatments to get it right again.
8. Brush and test daily. Brush a lot to prevent new algae growth on the walls. The chlorine should kill the algae for the next few days. Test daily to monitor chlorine and pH levels.
   • A well-maintained swimming pool has approximately the following values: chlorine: 2-4 ppm, pH: 7.2-7.6 ppm, alkalinity: 80-120 ppm and hardness 200-400 ppm. Small deviations are normal, so a little fluctuation is okay.
9. Vacuum up the dead algae. When the water is no longer green, vacuum up any dead algae until the water is clear. You can skip this step and leave it to the filter, but only if you have a powerful filter and are willing to wait a few days.
   • If you're having a hard time getting rid of all the algae, add a coagulant or flocculant to make them stick together. You can find this at pool specialty stores, but it may not be worth buying for a small pool at home.
10. Clean the filter. If you have a sand filter, set it to "backwash". If you have a cartridge filter, remove the cartridge and clean it with a pressure washer, possibly followed by dilute hydrochloric acid or liquid chlorine. If you don't clean the filter properly, it can get clogged with dead algae.

Method 2 of 3: Other ways to control algae

1. Improve flow to remove small amounts of algae. If small clumps of algae form and do not spread over the rest of the pool, the water may be standing still in certain areas. Check that the water jets are functioning properly. They have to end up in the pool at a certain angle so that the water moves in a spiral.
2. Catch the algae with a coagulant. A coagulant or flocculant ensures that the algae stick together, so that you can remove them from the water alive with a piston. This can take a hard day's work, but eventually your pool will be clean. This is the fastest way to keep your pool looking clean, but it makes it not safe to swim in it. If the algae can multiply, so can viruses and bacteria. After this, do a shock treatment to clean the pool, and do not swim in it until the chlorine and pH levels are back to normal.
3. Treat the pool with algaecide. Algicide certainly gets you rid of the algae, but the side effects and costs are a major drawback. Here are a few factors to consider:
   • Some algicides are not powerful enough to treat blooms, especially if you also have black algae. Ask a pool shop employee for help, or find a product with more than 30% active ingredients.
   • "Polyquats" are cheap, but it will foam your water. Many people find that annoying.
   • Copper based algicides are effective, but expensive. They also usually stain the walls of your pool.
   • After adding the algicides, wait at least 24 hours before adding any other chemicals.

Method 3 of 3: Prevent algae

1. Maintain your pool water well. You will not get algae if you keep a close eye on the composition of the pool water. Regularly test the pool for chlorine content, pH value, alkalinity and cyanuric acid. The sooner you tackle a problem, the easier it will be.
   • Daily testing is best, especially in the weeks after an algae infestation. Test at least twice a week during the swimming season.
2. Add algicides for prevention. Algicides are best applied in small, weekly doses when the water conditions are normal. Then they kill the algae before they can multiply. Check the product label for instructions.
   • Make sure you follow the directions for normal prevention, not those for an algae infestation. Using too many algicides can cause stains or foam in your pool.
3. Remove phosphates. Algae feed on various nutrients in the water, especially phosphates. You can use an inexpensive test to check whether there are phosphates in your pool water. If they are present, use a phosphate remover from a pool supply store. In the following days, remove the phosphate remover with the filter and a plunger. Then shock the pool.
   • Experts disagree on acceptable phosphate levels. 300 ppm is probably low enough, unless you keep having algae.

Tips

• Heat and sunlight break down chlorine so that algae can grow faster. Keep a close eye on chlorine levels during hot, sunny weather.
• Cover the pool in winter with a special tarpaulin that keeps out dirt, but allows water to pass through.
• If you have the time, add half of the chemical first and the rest a few hours later. Then you reduce the chance that you add too much, because that is difficult to correct.
• Keep a close eye on your pool filter throughout this process. Always clean the filter when the pressure is 10 psi above normal pressure. Dead algae can quickly clog the filter, so it should be cleaned regularly.

Warnings

• The pool cannot be used again until the algae are dead and the chlorine level has returned to a safe level of 4 ppm or less.