Introduction: Why Algae Is Every Pool Owner's Nightmare

Part One: Green Algae in Your Pool

What Is Green Algae?

Green algae, scientifically classified under the division Chlorophyta, is the most prevalent type of algae found in swimming pools. There are thousands of species of green algae in nature, and several of them thrive in pool environments when conditions are favorable. In a healthy, properly maintained pool, these algae are kept in check by chlorine and other sanitizers. However, when chemical levels drop or circulation falters, green algae can establish itself with remarkable speed.

Green algae typically appear first as a slight haze or tint in the water, often described as a pea-green or lime-green color. As the bloom worsens, the water can turn fully opaque and take on a deep emerald or even brownish-green hue. Algae may also appear as green slime or film on pool walls, steps, and floors, particularly in corners, shaded areas, and anywhere that water circulation is poor.

One distinctive characteristic of green algae compared to other types is that it is free-floating. It grows suspended in the water column rather than attaching firmly to surfaces, which makes it easier to treat but also means it can spread rapidly throughout the entire pool in a short amount of time.

What Causes Green Algae to Grow?

Understanding the root causes of a green algae outbreak is essential for effective treatment and prevention. Green algae does not appear randomly. It grows because specific conditions in your pool have made it possible for algae to take hold and multiply. Here are the primary causes:

Low or Inconsistent Chlorine Levels

Chlorine is the primary defense against algae growth in a swimming pool. When free chlorine levels drop below 1 part per million (ppm), the sanitizing protection becomes insufficient to kill algae spores before they can establish a bloom. This can happen for a variety of reasons, including heavy bather loads, hot weather, rain diluting the water, or simply forgetting to add chemicals on schedule.

Chlorine is constantly consumed as it sanitizes the water, reacting with contaminants, body oils, sunscreen, and organic debris. In warm summer weather, chlorine degrades particularly fast due to UV exposure from the sun. Outdoor pools can lose up to half their chlorine content in just a few hours on a bright, hot day without stabilizer (cyanuric acid) present in the water.

Poor Water Circulation and Dead Zones

Your pool pump and filtration system are responsible for keeping water moving, distributing chemicals evenly, and removing debris that feeds algae. When the pump is not running long enough each day, or when certain areas of the pool have poor circulation, stagnant zones develop. These dead zones are where algae love to settle and grow, because the sanitizer levels there are lower and debris accumulates.

Common dead zones in pools include behind ladders, in the corners of steps, behind skimmer baskets, and in any crevice or indentation. If your pool return jets are not angled correctly, or if your pool has an irregular shape with tight corners, some areas may simply not receive adequate water flow.

Imbalanced Water Chemistry

Chlorine works most effectively within a specific pH range of 7.2 to 7.6. When pH rises above 7.8, chlorine becomes significantly less effective as a sanitizer, even if the chlorine level reads correctly on a test. High pH is one of the most overlooked reasons for recurring algae problems. Additionally, low cyanuric acid levels (the stabilizer that protects chlorine from UV degradation) and imbalanced alkalinity can all compromise your pool's ability to fight algae.

High Temperatures and Sunlight

Algae are photosynthetic organisms, meaning they thrive with sunlight and warmth. During the hottest months of the year, when pool temperatures climb into the 80s and 90s Fahrenheit, algae growth conditions become near-ideal. Warm water holds less dissolved oxygen, chlorine degrades faster, and algae can double their population in a matter of hours under the right conditions.

Phosphates and Nitrates in the Water

Algae, like all living organisms, need nutrients to grow. Phosphates and nitrates are the primary food sources for pool algae. They enter pools through a variety of sources, including leaves, grass clippings, fertilizer runoff, rainwater, dirt tracked in by swimmers, and even some pool chemicals. When phosphate levels rise above 200 to 300 parts per billion, algae have an abundant food supply that makes them much harder to control even with adequate chlorine.

Algae Spores from Environmental Sources

Algae spores are present virtually everywhere in the outdoor environment. They travel on the wind, on swimsuits worn in natural bodies of water, on pool toys, on animals that may enter the pool area, and in rainwater. A single introduction of spores into an improperly maintained pool is all it takes to start a bloom within 24 to 48 hours.

How to Get Rid of Green Algae: Step-by-Step Treatment

Treating a green algae bloom requires a systematic approach. Skipping steps or rushing the process will result in incomplete treatment and a rapid return of the algae. Follow this process carefully for the best results.

Step 1: Test Your Water

Before adding any chemicals, test your pool water thoroughly. You need to know the current levels of free chlorine, pH, total alkalinity, cyanuric acid, and calcium hardness. This gives you a baseline and helps you understand which imbalances may have contributed to the algae bloom. Use a reliable liquid test kit or take a water sample to a pool supply store for a professional analysis.

Step 2: Clean the Pool Physically

Brush all pool surfaces vigorously with a pool brush. Brush the walls, floor, steps, and any corners or crevices. Brushing breaks up algae colonies and removes them from surfaces, making them easier for chemicals to reach and kill. Use a stiff-bristle brush for concrete or plaster pools, and a softer nylon brush for vinyl or fiberglass surfaces to avoid scratching.

After brushing, vacuum the pool. If the algae bloom is severe, vacuum to waste rather than through the filter to avoid clogging it. Vacuuming to waste means the water is expelled out of the pool entirely rather than recycled through the filter.

Also, clean out skimmer baskets and remove any debris such as leaves or organic matter from the pool. This reduces the organic load that consumes chlorine and feeds algae.

Step 3: Balance the Water Chemistry

Before shocking the pool, adjust the pH to between 7.2 and 7.4. This is the range at which chlorine is most effective. Adjust total alkalinity to 80 to 120 ppm if needed. Do not add clarifier or algaecide at this stage. Simply get the chemistry as balanced as possible to maximize the effectiveness of the shock treatment.

Step 4: Shock the Pool

Pool shocking means adding a large, concentrated dose of chlorine to the water to rapidly raise the chlorine level high enough to kill all algae and bacteria present. For a green algae bloom, you need to raise the free chlorine level to at least 10 ppm, and for severe blooms, up to 30 ppm.

Use calcium hypochlorite shock (cal-hypo) or sodium dichloro-s-triazinetrione (dichlor) for this purpose. Calculate the amount needed based on your pool's volume. As a general starting point, use 2 pounds of cal-hypo shock per 10,000 gallons for a light algae bloom, and up to 4 to 6 pounds per 10,000 gallons for a severe bloom.

Always shock the pool at dusk or after dark. Shocking in direct sunlight causes chlorine to degrade rapidly, wasting the treatment. Add the shock slowly around the perimeter of the pool while the pump is running. Never add shock directly to the skimmer.

Step 5: Run the Filter Continuously

After shocking, run your pool pump and filter continuously for at least 24 to 48 hours. Your filter is responsible for removing the dead algae particles from the water. If you have a sand filter, backwash it every 8 to 12 hours during treatment. If you have a cartridge filter, clean the cartridge. If you have a diatomaceous earth (DE) filter, backwash and recharge with fresh DE.

Step 6: Add an Algaecide

After the shock treatment, once the chlorine level has dropped back below 5 ppm, add a quality algaecide as directed on the product label. Algaecide is not a primary treatment for algae but serves as a supplemental preventive agent that helps break the algae's outer cell membranes and prevents regrowth. Look for algaecides containing polyquaternary ammonium compounds (poly-quats) for the most effective and foam-free results.

Step 7: Brush Again and Test

After 24 to 48 hours, brush the pool again to remove any remaining dead algae clinging to surfaces. Test the water again to check chlorine, pH, and other parameters. The water should be clearing and returning to its normal blue color. If it is still green or cloudy, you may need to shock again.

In some cases, a clarifier can be helpful at this stage to help clump together fine dead algae particles so the filter can capture them more efficiently. Continue running the filter and backwashing or cleaning as needed until the water is fully clear.

Part Two: Black Algae in Your Pool

What Is Black Algae?

Black algae is a completely different organism from green algae, and it presents a far more serious challenge for pool owners. Despite being called algae, black algae belongs to a group of organisms called cyanobacteria, which are photosynthetic bacteria rather than true algae. Understanding this distinction is critical because it explains why black algae is so much harder to kill than green algae.

Black algae appear as dark, round spots or patches on pool surfaces. These spots range in size from a few millimeters to several centimeters across, and they often have a slightly raised, bumpy, or rough texture. The color can range from dark blue-green to deep black, depending on the specific species and how established the colony is. Black algae are most commonly found on concrete, plaster, or gunite pool surfaces where they can physically embed themselves into pores and cracks in the material.

The most defining and troubling characteristic of black algae is its protective outer layer. Each colony of black algae produces a thick, waxy, protective coating over itself that acts as a shield against chlorine and other sanitizers. This coating prevents chemicals from penetrating to the living cells beneath, which is why simply shocking the pool or adding algaecide rarely eliminates black algae entirely.

What Causes Black Algae to Grow?

Black algae are introduced to pools in many of the same ways as other algae types, but they tend to establish themselves in pools with specific vulnerabilities. Once established, even a microscopic amount of surviving black algae can regrow into a full bloom.

Swimsuits Worn in Natural Bodies of Water

This is one of the most common pathways for black algae introduction. Cyanobacteria are extremely common in lakes, rivers, ponds, and the ocean. When someone swims in a natural body of water while wearing a swimsuit and then enters the pool without thoroughly rinsing and washing the suit, they can introduce billions of cyanobacteria spores into the pool water in a single swim.

Pool Surfaces with Rough Texture or Cracks

Black algae need a surface to anchor themselves. Smooth surfaces like fiberglass are far less susceptible to black algae because the organisms have difficulty attaching. However, rough or porous surfaces such as plaster, concrete, gunite, and even grout lines in tiled pools provide countless microscopic crevices where black algae can embed their root-like structures called rhizoids. Once the rhizoids penetrate into the surface material, the algae become extremely difficult to remove physically or chemically.

Inadequate Sanitizer Levels

Like all algae types, black algae require insufficient chlorine levels to establish themselves. However, unlike green algae, black algae can persist even in pools with otherwise adequate chlorine levels because of their protective coating. A pool that experiences periodic dips in chlorine levels gives black algae the opportunity it needs to entrench itself.

Poor Brushing and Maintenance Habits

Black algae spots that are small and newly formed can sometimes be managed with aggressive brushing and chemical treatment. However, when pool owners fail to regularly brush pool surfaces, particularly in corners, around steps, and along the waterline, black algae has the opportunity to grow from small spots into deeply embedded colonies.

How to Identify Black Algae vs. Other Pool Stains

Not all dark spots in a pool are black algae. Metal stains from copper or iron, dark calcium deposits, and dirt accumulation can all look similar at first glance. Before treating for black algae, confirm the identification using these methods:

• Texture Test: Black algae spots feel rough and bumpy when you run your hand or brush over them. Metal stains and calcium deposits feel smooth or flat.
• Chlorine Test: Apply a small amount of liquid chlorine directly to the spot using a squeeze bottle. If the spot lightens or temporarily disappears after direct chlorine application, it is likely algae. If it does not respond, it is more likely a mineral stain.
• Persistence Test: Black algae spots will return after brushing if not fully treated. Dirt or loose deposits will brush away easily and not return. Metal stains remain regardless of brushing.
• Color and Pattern: Black algae typically appear as distinct, circular spots with darker centers. They often appear in clusters and prefer shaded areas of the pool.

How to Get Rid of Black Algae: Step-by-Step Treatment

Eliminating black algae requires physical aggression, high chemical doses, and persistence. Even after the visible spots appear gone, microscopic black algae can remain alive beneath the surface and will regrow if not fully eradicated. Plan for a treatment process that takes several days to complete.

Step 1: Gather the Right Supplies

Before starting, make sure you have the following on hand: a stainless steel wire pool brush (for plaster or concrete surfaces), a concentrated trichlor-based algaecide or black algae-specific algaecide, calcium hypochlorite shock (at least 68% available chlorine), a trichlor tablet or stick for direct spot treatment, protective gloves and goggles, and a reliable water test kit.

Step 2: Brush the Spots Aggressively

Using a stainless steel wire brush, scrub every black algae spot vigorously. The goal is to break through the protective waxy coating. This will not kill the algae but will create openings that allow chemicals to penetrate to the living cells beneath. Brush each spot for at least 30 to 60 seconds, applying firm, consistent pressure. You may notice a dark cloud release into the water as you brush. This is normal.

After brushing, do not vacuum or disturb the water more than necessary. You want the loosened material to remain accessible to the chemicals you will be adding.

Step 3: Apply Trichlor Directly to the Spots

After brushing, take a full-strength trichlor tablet or stick and rub it directly on each black algae spot while underwater. Trichlor is an extremely concentrated, slow-dissolving form of chlorine. Applying it directly to the spot delivers a concentrated chemical blast that can penetrate the algae's defenses. This direct application is one of the most important steps in treating black algae and is one that many pool owners skip.

Step 4: Shock the Pool at Triple Strength

Black algae treatment requires a much heavier shock dose than green algae. Aim to raise the free chlorine level to at least 20 to 30 ppm. Use calcium hypochlorite shock with at least 68% available chlorine. For a 20,000-gallon pool, this typically means 6 to 8 pounds of cal-hypo shock or more, depending on current chlorine levels. Add the shock at night with the pump running.

Step 5: Add a Black Algae-Specific Algaecide

Once the shock is added and the pump is circulating, add a high-quality algaecide specifically formulated for black or resistant algae. Products containing copper-based compounds or quaternary ammonium compounds at high concentrations are most effective. Follow the product label for dosing based on your pool volume.

Step 6: Run the Filter and Brush Daily

Run your filter continuously for the next 72 to 96 hours. Brush the pool surfaces every single day, focusing particularly on areas where black algae spots were visible. Consistent daily brushing is critical because it re-breaks the protective coating as it attempts to reform, keeping the living algae cells exposed to the elevated chlorine in the water.

Backwash or clean your filter daily during this period. Black algae particles will be filtering out of the water, and a clogged filter dramatically reduces the effectiveness of your pump and reduces water clarity.

Step 7: Monitor and Repeat if Necessary

After 72 hours, assess the treated spots. In mild cases, the spots may have significantly lightened or disappeared entirely. In moderate to severe cases, you may still see dark remnants. Brush vigorously again, apply trichlor directly to remaining spots, and re-shock if the chlorine level has dropped below 10 ppm.

Black algae treatment often requires two to three rounds of shock treatment over the course of a week to ten days to fully eradicate the infestation. Do not reduce chlorine levels or stop brushing until you have confirmed there are no remaining dark spots and the pool has been clear for at least 3 to 4 days.

Step 8: Consider Surface Repair

If the black algae has been present for an extended period or has caused visible pitting or damage to the plaster surface, surface repair may be necessary after treatment. Deep algae staining or physical surface damage provides ongoing anchor points for future algae growth. A pool professional can assess whether resurfacing, acid washing, or patching is warranted.

Green Algae vs. Black Algae: Side-by-Side Comparison

The Complete Pool Algae Prevention Guide

The most effective strategy for dealing with pool algae is making sure it never has the opportunity to grow in the first place. Prevention is always less expensive and less labor-intensive than treatment. A well-maintained pool with consistent chemistry and good circulation will resist algae growth even in the hottest summer months.

Maintain Consistent Chlorine Levels

Keep free chlorine between 2 and 4 ppm at all times during the swimming season. Test your water at least two to three times per week, and daily during periods of heavy use, extreme heat, or after significant rain. Use a quality test kit or digital tester for accurate readings.

Consider using a chlorine feeder or automatic chlorinator to maintain a steady, consistent dose of chlorine rather than relying solely on manual addition. Chlorine feeders ensure your pool always has a baseline level of sanitizer, even on days when you forget to add it manually.

Maintain Proper pH at All Times

pH is arguably the single most important chemical parameter to keep balanced, because it affects how well chlorine works. Keep pH between 7.2 and 7.6 consistently. Test pH at every water test. High pH, which is above 7.8, dramatically reduces chlorine's sanitizing efficiency, effectively making your chlorine almost useless even when levels appear adequate. Sodium carbonate (soda ash) raises pH, while sodium bisulfate (dry acid) or muriatic acid lower it.

Use Cyanuric Acid (Stabilizer) Correctly

Cyanuric acid (CYA) stabilizes chlorine by protecting it from UV degradation. Without CYA in the water, outdoor pools can lose the majority of their free chlorine within a few hours of direct sunlight. The ideal CYA level for an outdoor pool is between 30 and 50 ppm. However, CYA levels that are too high, above 80 to 100 ppm, will actually reduce chlorine's effectiveness (a problem known as chlorine lock).

If CYA levels get excessively high due to overuse of stabilized chlorine products like trichlor or dichlor, the only way to reduce them is to partially drain and refill the pool with fresh water.

Run the Pump Long Enough Every Day

Proper water circulation is one of the most overlooked aspects of algae prevention. Your pump should run long enough each day to turn over the entire volume of your pool at least once, and ideally twice. As a general rule of thumb, run the pump for one hour for every 10 degrees Fahrenheit of air temperature. So on a day when the temperature is 90 degrees Fahrenheit, run the pump for at least 9 hours.

Make sure your return jets are aimed to create a circular, spiraling flow that reaches every corner of the pool. Aim jets slightly downward and at an angle to maximize surface agitation and reach dead zones.

Brush Pool Surfaces Weekly

Regular brushing is one of the most powerful preventive tools available to pool owners. Brushing disrupts algae colonies before they can establish themselves and removes biofilm from surfaces. Brush the entire pool weekly, paying special attention to corners, steps, behind ladders, along the waterline, and any area that receives less direct sunlight or water circulation.

For pools with plaster or concrete surfaces that have had black algae problems in the past, brush at least twice weekly as a preventive measure. Even a few seconds of brushing on former black algae spots during your regular maintenance routine can prevent regrowth.

Clean the Filter Regularly

A dirty or clogged filter cannot remove algae particles and debris from the water effectively. Sand filters should be backwashed when the pressure gauge reads 8 to 10 psi above the clean starting pressure. Cartridge filters should be cleaned every 2 to 4 weeks during peak season, depending on pool usage. DE filters should be backwashed and recharged with fresh DE powder regularly.

At least once per season, perform a deep clean of your filter. For cartridge filters, soak the cartridges in a filter cleaning solution overnight to remove oils, sunscreen residue, and mineral buildup that backwashing alone cannot remove. For sand filters, consider adding a sand filter cleaner to dissolve organic material embedded in the sand.

Shock the Pool Weekly or After Heavy Use

Routine weekly shocking, even when the pool looks perfectly clear, is an excellent preventive practice. A maintenance shock dose of 1 to 2 pounds of calcium hypochlorite per 10,000 gallons raises the chlorine level to 5 to 10 ppm, killing any algae spores before they can take hold. Always shock at night or in the evening.

Additionally, shock the pool after any of the following events: a heavy rainstorm (rain dilutes chemicals and introduces phosphates and algae spores), a large pool party with many swimmers (heavy bather load consumes chlorine rapidly), an extended period of very hot weather, or any time you notice the water beginning to appear slightly cloudy or hazy.

Use a Quality Algaecide as a Preventive

Adding a maintenance dose of algaecide every 1 to 2 weeks provides an additional layer of protection against algae growth. Poly-quat algaecides (polyquaternary ammonium compounds at 30 to 60 percent concentration) are the best choice for routine prevention because they are non-foaming, do not stain pool surfaces, and do not interact negatively with chlorine. Copper-based algaecides are effective but can cause staining on pool surfaces and should be used with caution.

Manage Phosphate Levels

If your pool is prone to recurring algae problems despite proper chlorine and pH maintenance, high phosphate levels may be the underlying cause. Test for phosphates and if levels are above 200 to 300 parts per billion, use a phosphate remover product to bring them down. Phosphate removers work by binding to phosphate molecules and causing them to precipitate out of the water, where they can be removed by the filter.

Reduce phosphate sources where possible by rinsing off before entering the pool, keeping vegetation trimmed away from the pool edge, minimizing fertilizer use near the pool area, and using a pool cover when the pool is not in use.

Wash Swimwear Before Swimming

Since swimwear worn in natural bodies of water is one of the primary pathways for black algae introduction, establish a household rule that all swimsuits worn in lakes, rivers, or the ocean must be thoroughly washed with detergent and hot water before wearing in the pool. This simple habit can significantly reduce the risk of introducing cyanobacteria and other resistant organisms into your pool.

Use a Pool Cover

A pool cover, particularly a solid safety cover or solar cover, provides multiple algae-prevention benefits. It keeps sunlight from reaching the water (reducing algae's ability to photosynthesize), prevents environmental algae spores, leaves, and debris from entering the pool, and reduces chemical evaporation and degradation. When the pool is not in active use, covering it is one of the most cost-effective preventive measures available.

Maintain Pool Chemistry Through Winter

In warmer climates where pools remain open year-round, algae prevention is a twelve-month concern. Even during cooler months, maintain appropriate chlorine levels and test water regularly. Algae grow more slowly in cold water, but they do not disappear entirely. A pool that is neglected during winter will enter the spring season with an established algae bloom that requires significant effort and expense to correct.

In climates where pools are closed for winter, use a quality winter closing kit that includes an algaecide and shock treatment appropriate for winterization. Properly balancing and treating the water before closing significantly reduces the likelihood of opening to a green pool in spring.

Frequently Asked Questions

How long does it take to clear a green algae bloom?

With prompt and thorough treatment, a mild green algae bloom can clear up within 1 to 3 days. Moderate blooms may take 3 to 5 days. Severe, deeply established blooms can take 5 to 10 days or longer, particularly if the filter needs repeated cleaning to handle the large volume of dead algae particles.

Can I swim in a pool with algae?

Swimming in an algae-infested pool is not recommended. While the algae itself may not cause direct illness in healthy individuals, the bacteria that thrive alongside algae, including harmful pathogens, can cause skin rashes, ear infections, eye irritation, and gastrointestinal illness. Additionally, during shock treatment, chlorine levels are far too high for safe swimming. Wait until the pool is visually clear, chlorine has returned to 1 to 3 ppm, and pH is balanced before allowing anyone to swim.

Will pool shock alone kill black algae?

No. Pool shock alone is insufficient to fully eliminate black algae because the organism's protective waxy coating prevents chlorine from reaching the living cells. Effective black algae treatment always requires aggressive physical brushing to break through that coating, combined with direct trichlor tablet spot treatment, a triple-dose shock, and a concentrated algaecide. All of these steps must be performed together for reliable results.

What is the difference between cloudy water and a green algae bloom?

Cloudy water can result from several causes other than algae, including high calcium hardness, poor filtration, imbalanced pH, or very high chlorine levels causing particles to precipitate out of solution. A green algae bloom will have a distinctly green tint to the cloudiness and is usually accompanied by green slime or film on pool surfaces. Cloudy water without any green tint is more likely a chemistry or filtration issue. Testing the water will help identify the actual cause.

Can algae damage my pool surface?

Yes, particularly black algae. Over time, the rhizoids (root-like structures) of black algae can physically penetrate and damage plaster, concrete, and grout surfaces, creating pitting and etching that not only looks bad but provides permanent anchor points for future algae growth. Green algae can stain pool surfaces, particularly porous ones, and can produce organic acids that slowly degrade plaster over years of repeated blooms.

How do I know if all the black algae has been eliminated?

After treatment, continue brushing daily and inspect the treated spots carefully. True elimination is confirmed when the dark spots do not return after 5 to 7 days of observation following the last treatment. If spots reappear, even as faint shadows or small dots, the algae has not been fully eradicated and treatment must be repeated. Remember that microscopic algae cells anchored deep in the plaster can regrow from nearly invisible remnants.

Is it safe to acid wash a pool to remove black algae?

Acid washing is a powerful and effective method for removing deeply embedded black algae and algae staining from plaster pool surfaces. However, it is a serious procedure that drains the pool completely and uses diluted muriatic acid to etch the top layer of plaster. Each acid washing removes a small amount of the plaster surface and can only be done a limited number of times before the plaster must be replaced. Acid washing should be performed by a qualified pool professional and is typically reserved for severe cases where standard treatment has failed.

Conclusion: Winning the Fight Against Pool Algae

Dealing with green and black algae in your pool is one of the most common challenges that pool owners face, but it is a challenge that can absolutely be overcome with the right knowledge, the right tools, and consistent effort. Green algae, while unsightly and disruptive, responds well to prompt treatment with proper shocking, brushing, and filtration. Black algae demands a more intensive, multi-day approach that combines aggressive physical treatment with elevated chemical doses and diligent follow-up monitoring.

More important than any treatment, however, is prevention. A pool that receives consistent, attentive maintenance, with balanced chemistry, adequate chlorine, proper circulation, and regular brushing, will rarely if ever experience a significant algae bloom. The time investment in regular preventive care is a fraction of the time, effort, and expense required to treat an established algae problem.

By understanding the biology of these organisms, recognizing the early warning signs, and applying the treatment and prevention strategies outlined in this guide, you can keep your pool sparkling clean and inviting throughout the entire swimming season and beyond. A little knowledge and consistent effort go a very long way toward keeping algae out of your pool permanently.