From Pond to Garden: Using Pond Scum as Natural Fertilizer

 

One man’s pond scum is another man’s treasure. Some biological waste from your pond can be beneficial to your backyard. The sludgy green algae, that you work so hard to prevent and get rid of, is a perfect and essential ingredient in composting. Compost is an organic, natural, and cost-efficient way to fertilize plants and soil.  So now when you are clearing out that algae, you can put it to good use. 

 

Why Pond Scum Works in Compost  

Spring is a popular time to clean your pond, but late summer and early fall are also ideal for starting compost. These seasons give your pile time to break down before winter, so it’s ready to enrich your garden beds come spring planting.  

Composting transforms organic material into a dark, nutrient-rich substance that conditions the soil. This “soul of healthy soil” helps plants grow stronger, improves water retention, and reduces nutrient runoff. 

 

The Benefits of Pond Algae in Compost  

  • Rich in Nitrogen: Algae provides an excellent source of nitrogen, a key fuel for composting bacteria. 

  • Added Nutrients: Pond scum introduces potassium and phosphorus into the pile, further boosting soil health. 

 

How to Turn Pond Waste into Compost 

Step 1: Remove and Prepare Pond Scum 

  • Use a fish net, pool skimmer, or rake to collect algae from your pond. 

  • Drain excess water. If the pond is salty, rinse the algae with fresh water before composting. 

Step 2: Gather Green and Brown Materials 

  • Green (nitrogen-rich): fresh grass clippings, manure, coffee grounds, vegetable scraps, and pond algae. 

  • Brown (carbon-rich): straw, shredded paper, dead leaves, dried grass, cardboard, or old hay. 

Step 3: Layer Your Compost Pile 

  • Spread 4–6 inches of carbon-rich material as the base. 

  • Add a 3-inch layer of green material (including pond algae). 

  • Sprinkle plain topsoil over the pile to introduce helpful bacteria. 

  • Lightly moisten with a garden hose. 

  • Continue alternating layers until the pile is 3–4 feet tall. Push the center down slightly to help collect rainwater. 

Step 4: Maintain Your Compost 

  • Within 24 hours, the pile should begin heating. 

  • Check moisture every 2–3 days. It should feel like a wrung-out sponge. 

  • After 4–5 weeks, turn the pile with a manure fork to aerate it, repeating every 7–10 days. 

When Your Compost Is Ready 

After several weeks, the pile will turn dark brown with a crumbly texture and earthy smell. At this point, you can: 

  • Spread up to 3 inches of compost over garden soil before planting. 

  • Use it as mulch to retain moisture. 

  • Mix it with perlite or coarse sand to create potting soil for containers or houseplants. 

The Rewards of Composting Pond Scum 

Using pond scum as fertilizer helps save money on commercial fertilizers, reduce waste and pollution, and build healthier soil for a thriving backyard garden. It also gives you a productive late summer or fall project that benefits both your pond and your landscape. 
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