Every summer the calls start. The pond that looked perfect in May has turned green, the water is cloudy, and the rocks feel slick. Central Iowa summers, with their heat, long daylight, and nutrient runoff, are prime conditions for algae. The good news is that a properly built ecosystem pond has the tools to handle it, and most green-water problems trace back to a few fixable causes.
Why ponds turn green
Algae is not a disease. It is a plant, and like any plant it grows when it has light and nutrients. In summer, our long, hot days deliver plenty of light, and excess nutrients come from fish waste, uneaten food, decaying leaves, and lawn fertilizer runoff. When nutrients outpace what the pond's natural systems can absorb, algae blooms.
The two kinds you will see
Green water is a suspended single-cell algae that clouds the whole pond. String algae is the hair-like growth that clings to rocks and waterfalls. They have different fixes, so it helps to know which you are fighting.
Restore the balance, do not just kill it
Reaching for an algaecide every time is treating the symptom. A balanced pond controls algae through competition and filtration.
- Add more aquatic plants, which compete directly with algae for the same nutrients and shade the surface.
- Do not overfeed fish, since uneaten food and extra waste become algae fuel; feed only what fish finish in a few minutes.
- Keep the filter and skimmer clean so they can actually remove the nutrients driving the bloom.
- Keep beneficial bacteria dosed through the warm months to break down the organic material algae feeds on.
- Add aeration, since moving, oxygenated water supports the bacteria and fish that keep the system in balance, especially during heat waves.
When to bring in help
If your pond stays green despite good habits, the issue may be undersized filtration, too many fish, or a build that was never balanced correctly. That is where an exploratory drain and clean, or a filtration upgrade, resets the whole system. We handle these across the metro all summer, and we can usually tell you the root cause on the first visit rather than selling you another jug of chemicals. Clear water is the natural state of a well-built pond.
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