"Why is my pond green?" It's a question we hear a lot from pond owners, and the answer is algae. Green water and string algae are a common problem for many pond hobbyists. But what causes algae in ponds?
Algae is a result of an imbalance in your pond's ecosystem. When too many nutrients caused by decomposing plant material, fish waste, or other debris build-ups in your water garden, algae will flourish because the nutrients act as a fertilizer. Identifying the underlying problems that are causing the algae bloom in a pond and working towards solutions are key to achieving a clean and balanced pond that will keep your neighbors green with envy.
Problem: Too Many Fish
Solution: As it turns out, one of the primary causes of algae in fish ponds are the fish. They are a great addition to any pond, but if your water garden is brimming with fish, it may be time to relocate some of them. overcrowding can easily happen as your fish grow through the years and reproduce. Not only will your fish have tight living conditions, but your filter system may not be large enough to handle the waste being produced. A simple rule of thumb it to allow 1-2 koi or 2-3 goldfish per 200 gallons of water.
Problem: Debris Build-Up
Solution: Leaves, fish waste, and other organic material accumulate in a pond. Cleaning your pond in the spring is a great step toward preventing algae blooms in ponds. Our spring pond care guide will help you through the process step by step. Throughout the season, use a pond vacuum to help keep it tidy. In the fall, we do not recommend giving your water garden a deep clean unless it really needs it.
Problem: Not Enough Mechanical Filtration
Solution: Mechanical filtration helps to remove the excess nutrients from the water column. As the water passes through the pond filter, debris is removed and collected in the filter box or skimmer. Filters are rated based on the pond size, but for water gardens with high fish loads, a larger filter may be needed.
Problem: Lack of Beneficial Bacteria
Solution: Beneficial bacteria, like those found in the DefensePAC, are microorganisms that consume excess nutrients and debris and convert them into a harmless gas. When there are little to no nutrients to feed the algae in a fish pond, it will eventually die off. Beneficial bacteria cultivate on surfaces, such as your filter pads. Cleaning your filter pads too much – meaning daily or weekly – can wash away your beneficial bacteria. Instead, lightly rinse the pads if the water is unable to pass through the filter.
Problem: Inadequate Aeration
Solution: Beneficial bacteria – as well as your fish – rely on oxygen to survive. Waterfalls and fountains can provide some aeration, but they may not sufficiently infuse oxygen into the pond. That is where pond aeration kits come into play. These systems force air through a diffuser or air stone, circulating the water and increasing your pond's dissolved oxygen levels. Learn more about the importance of aeration by clicking here.
Problem: Too Much Sunlight. Not Enough Plants.
Solution: Sunlight is essential for algae to grow. You can block that sunlight by covering your water with pond water lilies or other floating plants; we recommend shading 40-60% of your pond's surface area. Another benefit to adding plants is that they absorb the nutrients in the pond, helping prevent algae blooms.
We hope this guide was a helpful tool to learn how to keep algae out of a pond and control it if it does appear. If you have additional questions about how to prevent an algae bloom in your pond, don't hesitate to reach out to our team of experts for assistance.