Learn the best methods for getting rid of pond scum and maintaining a healthy water feature. Contact Living Water Aeration for personalized recommendations and solutions.

How To Get Rid of Pond Scum

That shiny slick of muck marring your pond’s surface - while perhaps confused for oil at a passing glance - points to a deeper ecological imbalance brewing below. 

Pond scum represents an overgrowth of several strains of algae that feed and reproduce readily in degraded water conditions. Left unchecked, rapidly multiplying algal colonies form green soupy layers on the water’s surface with detrimental effects.

But here’s the good news – with proper identification and treatment, pond scum can be conquered without harming delicate aquatic life. 

By addressing root causes like excess nutrients, poor circulation, and missing checks and balances, your water feature can regain its clarity and health - supporting plants, fish, and other wildlife for years to come. Let’s dive into building pond equilibrium that keeps the surface slick-free.

What Is Pond Scum?

When you hear “pond scum,” think of the thick, floating algal masses that accumulate on the water's surface when specific algae reproduce and bloom rapidly. There’s actually more than one type of algae that can cause scum, but the most common culprits are blue-green algae (cyanobacteria) and green water algae.

  • Green Algae - Suspended green particles that cluster together in response to light and nutrients. Most common contributor.

  • Filamentous Algae - Algae that grow in long hair-like strands, forming floating mats. Hard to control and remove once established.

  • Cyanobacteria - Primitive bacteria that function like algae through photosynthesis, thriving in warm, nutrient-dense water. Also called blue-green algae, although part of the bacteria kingdom. Can produce toxins that are harmful to wildlife.

Such algae are vital to a pond’s ecological balance in small amounts. But excessive growth causes several cascading issues:

  • Oxygen Loss - Dense algal blooms prevent oxygen exchange at the surface while also consuming oxygen nightly, leading to depletion.

  • Toxins & Illness - Certain blooms associated with toxic compounds that irritate skin and sicken aquatic life when cell walls rupture.

  • Odors & Aesthetics - Mass decay creates unpleasant odors and unsightly appearance.

What Causes Pond Scum?

Part of knowing how to get rid of pond scum starts with knowing why it’s shown up in your pond. In general, pond scum represents a biological indicator that environmental conditions favor excessive algal growth over other life forms. Typical triggers include:

Excess Nutrients - High nutrient input from sources like lawn fertilizers, pet waste, and debris accumulation, coupled with low nutrient uptake from fewer native aquatic plants, allows algae to exploit surplus nutrients to outcompete organisms.

Sunlight - Excess light enabled by reduced shade from fewer native plants, trees, etc., fuels photosynthesis and heating that accelerates algal growth and reproduction.

Low Oxygen - Stagnant zones created by poor circulation prevent gas exchange, favoring floating algal species able to access atmospheric oxygen and carbon dioxide.

Imbalance - Missing algae grazers like fish and aquatic invertebrates remove a key check on algal growth. Stocking cool-water fish species can help control insects that feed algae.

pH Fluctuation - Dramatic pH shifts can spur more resilient algae to exploit conditions less ideal for animals and beneficial microbiota that would otherwise keep algae in check.

Strategies for Pond Scum Removal

Once underlying causes are addressed, a combination of mechanical removal and biological control clears existing pond scum and prevents recurrence.

Mechanical Removal

Manual Techniques – For smaller ponds, manually scooping out free-floating algal mats using long-handled nets quickens recovery. Skim off accumulated organic debris regularly as well. Dispose of compost piles, not back in the pond.

Water Changes – Partially draining ponds through pumps or siphons removes built-up nutrients and algal cells, followed by refilling with fresh water. Reduce feeding for days following to limit nutrient replenishment.

Fountains & Aerators – Adding aeration through spray fountain features or bubblers oxygenates while circulating the entire water column. Prevents future stagnant zones prone to algal takeovers.

Biological Solutions

Barley Straw – Added loose or wrapped in nets, barley straw gradually releases mild natural algaecide as it decomposes over 6-8 weeks. Continually replenish on this cycle.

Beneficial Bacteria – Specialized bacteria supplement outcompete algae for nutrients while breaking down organics. Couple with adequate filtration systems for low-maintenance results.

Blackouts – Blocking sunlight completely using tarps or dyes for 2-4 days causes a blackout effect - crashing existing algae and letting animals and plants recover in its absence before it regrows.

An integrated approach reduces immediate pond scum while developing a lasting equilibrium that minimizes recurrence.

Preventive Measures and Pond Maintenance

While active removal tackles current pond scum, the best way to get rid of that unwanted scum for good is to take steps to prevent its growth in the first place. This can be achieved through proper pond maintenance and implementing preventive measures.

Reduce Nutrient Loading

Cut back on pond feeding and use phosphate removers to limit nutrient availability. Remove decomposing plant debris before it releases nutrients through decay.

Selective Planting

Grow beneficial pond plants favoring clear water, including anacharis, water lettuce, and hyacinths, which uptake nutrients and create shade.

Balance Wildlife Stocking

Keep algae grazers like koi and black mollies at stocking levels that suit your pond size. Their grazing and foraging keep algae in check and offer natural alternatives to chemical treatments.

Monitor Water Chemistry

Test for pH, nutrients, and temperature changes monthly or after heavy rains using home kits. Make adjustments before shifts trigger algal blooms – and make sure you don't shock your fish!

Clean Filters & Pumps

Keep equipment working optimally to maintain circulation and nutrient export, preventing stagnant conditions favorable to algae. When you keep your pond clean and chemically balanced, it can become a thriving ecosystem that supports diverse wildlife and plants.


How do you control pond scum naturally?

Promoting aquatic plant growth, reducing fertilization, managing wildlife stocking, and improving circulation can all create the right habitat balance to inhibit pond scum growth naturally without algaecides in most cases.

What eats pond scum and can help control it?

Various algae-eating species help control pond scum through grazing, including:

  • koi
  • livebearers like mollies and guppies
  • tadpoles/frogs
  • snails
  • crayfish

Balancing their stocking rates limits algal growth while maintaining water quality.

Is pond scum ever beneficial?

In moderation, algae represent a vital component of the pond food web. In balance with plants and algae consumers, algal plankton generates oxygen while providing essential nutritional forage for various aquatic insects and small fish species when limited. Some levels support life, but excess causes harm to the ecosystem.

Get Rid of Pond Scum for Good with Living Water Aeration

While a slick of green goo may prompt panic, pond scum blooms signify deeper opportunities - a chance to re-assess the current state of your water feature’s ecological checks and balances. 

Through proper identification, tracking down root causes, executing removal methods, and centering consistent preventative care, pond scum can be curtailed and kept under control without sacrificing aesthetics or recreation value. Consider seeking professional consultation to efficiently restore balance suited to your landscape vision.

For personalized recommendations on ideal pond scum treatment plans and water quality improvement products for your unique water feature – including aeration, beneficial bacteria, nutrient controls, test kits, and more – contact the team at Living Water Aeration and find our comprehensive line of pond and lake management solutions!
You can see our products
See Products
Back to blog

Leave a comment

Please note, comments need to be approved before they are published.