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Why Do Ponds Change Color? (Red, Black, and More)

Why Do Ponds Change Color? (Red, Black, and More)

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A pond on your property can offer several benefits, from aesthetics to temperature regulation.

However, you won’t probably feel the same about it if the water turns red, black, brown, green, or yellow. So why do ponds change color?

Pond water can change color for a number of reasons, including decaying debris, leaks, algae, and even soil turbidity.

In this article, we’ll address your inquiries about what caused the color shift in your pond’s water. We’ll also include some practical solutions to deal with the issue.

So, be sure to read until the last section of this post!

Why Does Pond Water Turn Red?

Three possible reasons your pond turns red are tannin, red algae, and minerals.

Here’s how they can affect the water:

1 – Red Tannins

Tannin is an organic compound that can give water a reddish tint. When organic materials with red pigments get into the pond and rot, the colors dissolve and dye the water.

For instance, leaves, bark, seeds, stems, and roots of mahogany, redwood, maple, purple beech, and cedar trees can be possible culprits.

2 – Red Algae

Red algae are more prevalent in seawater. In rare cases, they may start growing in a freshwater pond and make it look like the water itself is red.

3 – Minerals

Substances such as iron oxides may impact the water’s coloring if the pond is in an area rich in these minerals. Moreover, iron can also turn the rocks red.

So, if no signs of red algae or debris are present, a leak in the pond liner may be the reason behind the red water.

It’s possible that some minerals from the ground made their way into the pond and changed the color of the water. If so, you need to locate the leak as soon as possible and fix it.

Why Does Pond Water Turn Black?

The muck buildup of decomposing organic matter at the pond’s bottom is the most common cause of black water.

This mixture may also contain dead bacteria, algae, and rotting leaves. So, if this black goo isn’t addressed immediately, it can emit unpleasant smells.

Why Does Pond Water Turn Brown?

Sometimes, the pond water can turn brown due to the weather. For instance, strong winds may carry soil particles to your pond and “stir” the water, affecting its color.

However, if it turns brown when the weather is good, there might be a problem you need to investigate.

For one, brown water may be due to dead plant debris, like leaves and bark pieces that have fallen into the water or rotten algae sitting at the bottom of the pond. That’s because the rotten parts can emit brown tannins, which dissolve in the pond and affect the color.

Meanwhile, loose soil from weathering and erosion could also be why your pond changes color, and you can test the water to find out the cause.

To do this test, take some water from the pond and put it in a transparent container. Then, leave it for an hour or so and check what will happen.

If particles are sinking and settling at the bottom, then it’s due to the loose soil. However, if the water doesn’t change its color, the coloration could be caused by tannins.

Why Does Pond Water Turn Green?

Planktonic algae and bacteria can turn any body of water, including ponds, green. Algae bloom when the water has high phosphate and nitrate levels.

Too many fish in the pond can lead to more waste, which may increase nitrate levels. Moreover, the anaerobic sludge breakdown at the bottom of the pond also releases nitrogen and phosphorus.

Therefore, if the pond water is full of green algae, it’s likely that muck has started to build up at the bottom, providing nutrients for them to grow.

Why Does Pond Water Turn Yellow?

Your pond water might turn yellow if there are sources of yellow tannins in the area, such as oak trees.

Another possible cause is a high level of ammonia, which may result from high temperatures, overpopulation of fish, and overfeeding them. However, unlike tannins, ammonia is toxic and can be dangerous to fish.

If you have some fish in the pond, they might give you hints if the water has high ammonia. For example, they might seem stressed, lose their appetite, fall into comas, or die.

Is Colored Pond Water Dangerous?

Seeing a color change in your pond isn’t always dangerous, but it depends on what caused the discoloration. For instance, if tannins cause the difference, it’s not necessarily harmful.

However, high levels of ammonia or minerals can be dangerous. Some types of red algae might also be toxic to fish and other animals living in the pond.

What Can You Do if Your Pond Water Changes Color?

There are various ways to clarify and maintain your water, but you must determine the root cause first.

Then, you can treat your pond by combining any of these methods:

Method 1: Clean the Pond Area

Using a pond net, remove any floating debris on the pond’s surface. Fallen leaves, algae, and other similar materials are the leading sources of tannins, so you need to eliminate them.

After that, you can clean the pond liner with a vacuum. Letting sludge settle in the pond may create more problems with the water quality.

Don’t forget to check if your filter is working. You can also install a pond skimmer to help you further maintain the area.

Method 2: Treat Tannins

You may treat tannins using products like pond filter pads and activated carbon.

If these products don’t work, you might have to change the water and start maintaining your pond after that.

Here’s how:

  1. Drain your pond completely.
  2. Clean the pond area by removing any debris.
  3. Refill your pond.
  4. Dechlorinate the water, then wait for 24 hours.
  5. Put your fish back if you have some.

Method 3: Check for Leaks

If you think that the reason for your pond water’s color change is a particular mineral, you must check for leaks immediately.

Minerals may get into your pond if the liner is damaged. In that case, you’ll need to change it.

Method 4: Prevent Algal Growth

Using an ultraviolet clarifier can help you control algae growth in your pond.

Plus, if your pond is in an area with enough sunlight, there’s a greater chance of an algal bloom. So, adding some plants can create shade and absorb the nutrients algae typically consume.

You can combine floating, marginal, deep water, and bog plants. Here are some plants you might consider adding to your pond:

  • Water lily
  • Scarlet monkeyflower
  • Taro plants
  • Water lettuce
  • Sweet flag plant

Method 5: Install a Pond Net

Covering your pond area with a net can help you save time and effort in maintenance.

The net will keep any debris from falling into the pond. Without all the waste buildup, you can prevent tannins and sludge from affecting the water’s color.

Final Thoughts

A clear pond can give a relaxing feeling to any area, but a change in color can be worrisome.

Since there are various reasons why ponds change their color, you’ll need to identify the culprit first before deciding which clean-up method will work for your pond water.

Still, the best thing you can do after fixing the issue is to maintain cleanliness in the area.


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