Why Does Pond Water Turn Red?

Ponds are bodies of water that are smaller than lakes or creeks, but larger than streams. Ponds are often found in forests, marshes, fields, lawns, and other open spaces. They can vary in size from a few feet to over 100 acres. A pond is surrounded by land on all sides and the only way water can leave is through precipitation or by overflowing.

Pond water can turn red for a number of reasons. One way this happens is when the water contains a lot of decomposing plant material. This material, which is often seen as a thick sludge on the bottom of the pond, will eventually break down and release a chemical called tannin. Tannin gives the water a reddish-brown color or shade.

Another reason for red-colored water is blue-green algae, also known as cyanobacteria. This is the single most common cause of harmful algal blooms (HABs). This is a large, dense green algae that can grow very quickly (usually within days to weeks).

The red color can originate also from tannins, which are natural wood chemicals found in the waterway system, as well as tannin-containing leaves and bark on land masses nearby. Tannins mix with oxygen and sunlight to form a chemical called tannic acid.

What is an algal bloom?

Every summer, the water in our pond turns red. What is happening? If you’ve ever seen an algal bloom before, then you know what’s happening.

fish pond waterfall videos
fish pond waterfall videos

The pond water is turning red because there are massive amounts of microscopic phytoplankton called Cyanobacteria living there. These tiny organisms are not harmful to humans and cannot be seen without a microscope, but they can give off a strong odor that smells like rotten eggs.

Types of algae in a pond and their effects

Algae is found in most ponds and lakes. There are many types of algae, which can range from harmless to toxic. The kind of algae found in a pond depends on the type of water (fresh or salt), pH level, and nutrients present. All of these factors can influence the type of algae that grows. Some algae are toxic, and others are helpful.

Toxic algae can be harmful to fish and other organisms in the pond or lake. The toxicity of algae also depends on the type of algae. Some algae are edible, and others are poisonous.

In a freshwater pond, the most common toxic algae are called cyanobacteria. These are red or blue-green algae, which produce toxins in the spring and summer. These toxins can be deadly to birds, fish, and other animals.

Sometimes, the blue-green algae can cause water to turn a dark color, but it’s not always the case. Most of these algae have a gelatinous coating on them.

Red Pond
Red Pond” by flöschen is licensed under CC BY 2.0.

Algae and other water-based microorganisms

Pond water turns red because algae and other water-based microorganisms have a blue pigment that absorbs light, which then causes the release of red light. This is called cyanobacteria, or more commonly “red tide”.

The red tide algae is a group of bacteria that live in the ocean, freshwater, and on the land. The name red tide is used because the algae release chemicals that cause a red color when the sun shines on the water. The red tide bacteria is one of the ocean microorganisms. The term red tide is not used for other water-based microorganisms.

When and why pond water turns red?

When pond water turns red, it means that the bacteria have become oxygen-deprived. This could be because of an overabundance of algae blooms, seasonal changes or floodwaters.

Why does pond water turn red?

The color of pond water is influenced by two factors: the temperature and the rate at which oxygen dissolves into the liquid. When pond water turns red, it means that the bacteria have become oxygen-deprived.

Why does red water turn blue?

There are millions of oxygen-deprived bacteria in the pond. As they die, they release the oxygen they have stored. This oxygen combines with blue-colored dissolved substances from the water to form a blue-colored solution.

Why is it possible to see algae in a pond?

Algae are not plants, but only one of over 100,000 different kinds of single-celled organisms. They are simple organisms that absorb sunlight and use that energy to manufacture sugar, which they store in their cells. The sugar they manufacture is food for the bacteria in the pond. The algae also use water as a process of transportation.

Types of Algae can be found in Ponds

  • Green Algae: These have a green color and are usually found in ponds with a high food supply. Green algae are also called “slime algae” because of their slimy appearance. They can grow very fast and they are considered to be the worst kind of algae.
  • Brown Algae: These are also called “moss algae” because of their moss-like appearance and because they are very common in ponds that are fed with animal and vegetable waste. These are the most common type of algae and are often associated with organic waste.
  • Red Algae: These are also called “coral algae” because of their coral-like appearance. They are usually found in ponds with a high nutrient level.
  • Yellowish Algae: These are usually found in ponds that are not fed with water. They have yellowish in color. They are usually harmless.
  • Brown Stringy Algae: These are usually found in ponds with a high nutrient level. They are usually associated with organic waste. They have brown to dark brown color.
  • Black Thread-like Alga: This algae is usually found in ponds that have a high nutrient level. They have black in color and can be very dangerous. It is usually associated with organic waste.
red pond
red pond” by Brenda Anderson is licensed under CC BY-NC-SA 2.0.

What is the effect of algae in ponds?

Algae in ponds are beneficial for plants in the pond because they provide plants with nutrients when they decompose. Pond water will turn red when algae begin to decompose, but this is just a temporary effect that occurs when oxygen levels in the pond decrease. When oxygen levels fall, the algae will begin to decompose and release oxygen into the pond. Algae also produce oxygen when they decompose. The algae that decompose the most are those that are the most visible. This is usually the green-tipped algae.

Is red algae in a pond bad?

In areas where there are high levels of nitrogen, phosphorus or other nutrients in the water, algae will thrive and turn the water red. Some people think that this is bad for ponds and lakes because it blocks sunlight from reaching fish and plants below the surface, but others argue that the red algae provide food for aquatic animals that live in these waters.

Red algae is a type of algae that can thrive in a pond’s environment when there are high levels of nutrients. Red algae can also grow well in bodies of water where there is little sunlight.

How do I reduce algae in my pond naturally?

Ponds full of algae, also called a “pond bloom,” is a sign that something in your pond is out of balance. There are many different types of algae, but typically the reddish-yellow type is indicative of overfeeding abundance of sunlight, or lack of oxygen.

Ponds naturally produce algae as part of the ecosystem. Algae use sunlight for energy and help keep pond waters clean by producing oxygen through photosynthesis. You can reduce algae in your pond naturally by limiting the amount of sunlight that your pond receives.

How do I prevent algae from coming back after I do something to reduce it?

Algae will return to a pond or lake once the pond or lake suffers an algae bloom.

There are a few different ways to prevent algae from returning to your pond.

  • Increase Pond Size – You can increase pond size to prevent algae from returning to your pond. It is best to do this before the pond suffers an algae bloom. Increase pond size if you are able to do so, or if you have a large enough area for a new pond.
  • Add Mulch – You can use natural materials such as wood chips, ground bark, and leaves to prevent algae from returning.
  • Pond Treatment – You can use a pond treatment product to prevent algae from returning.

How to get rid of planktonic algae?

You can get rid of planktonic algae by adding oxygen to the water. This will allow the algae to die.

Intermittent aeration – This is the process of introducing air into the pond via an aerator. This process will keep the water oxygenated for an extended period of time.


Beginning with a catchy sentence to grab the reader’s attention, I will explain why there is so much color in a pond. One of the many organisms in a pond is algae. Algae give the water its red appearance due to it being a photosynthesizing organism. The algae also give off oxygen and produce organic acids, which makes the water more acidic.

Many people have wondered why their pond water has turned red or sometimes brown or green. The algae is usually the cause, although there are other causes as well.