String algae (filamentous algae)
Long, stringy algae that forms floating mats on the pond surface.
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Clear, green-free water starts here
Whether you're dealing with a full-blown algae bloom or trying to prevent one, this is your complete guide to understanding, treating, and controlling pond algae.
What is pond algae and why does it keep coming back?
Algae are microscopic, plant-like organisms that thrive in nutrient-rich, sun-exposed water. In small amounts they are natural. In large amounts they cloud your water, deplete oxygen, and stress your fish. The good news: once you know what is feeding the algae, the fix becomes clear.
What Type of Algae Do You Have?
Before you treat, you need to know what you are dealing with. The two most common types of pond algae look different and respond to different treatments.
Green water algae (planktonic algae)
Microscopic algae that can turn pond water green and cloudy.
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Already dealing with a bloom? Here is how to clear it up quickly. Start with the right treatment for your algae type and follow the steps below.
Treat with Algaecide
Works on both green water and string algae. Safe for fish and plants. For warm weather, space doses 5 to 7 days apart.
Add UV clarification
A UV clarifier neutralizes free-floating algae cells as they pass through, clearing green water at the source. Best for planktonic algae.
Keep water moving
Moving water adds oxygen, reduces the stagnant conditions algae thrives in, and helps treatments circulate more effectively.
How to Prevent Pond Algae From Coming Back
Treating algae clears the immediate problem. Preventing it keeps it from returning. These are the habits and products that make the biggest long-term difference.
Keep Water Moving
Stagnant water is algae's best friend. Add circulation to keep algae from establishing.
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Upgrade your FIltration
A filter with UV clarification neutralizes free-floating algae cells before they take hold.
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Add Aquatic Plants
Plants compete with algae for nutrients. Cover 2/3 of the pond to deprive algae of sunlight.
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Prevent Algae Naturally
Our treatments work together to keep nutrient levels low and algae growth in check.
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How Pond Algae Affects Your Fish
Algae blooms compete with fish for oxygen, especially overnight when algae stops producing it and starts consuming it. Heavy blooms can drop oxygen levels fast enough to stress or kill koi and goldfish. If your fish are gasping at the surface, an algae bloom may be the cause.
Algae Control Products That Work
From natural prevention to fast-acting treatment, these are the products pond owners reach for most.
