Why Your Garden Pond Has Turned Green and How to Fix It

Why Your Garden Pond Has Turned Green and How to Fix It

Green pond water is caused by algae. It’s one of the most prevalent problems with ponds, and it may be tough to regulate at times. Thankfully, there are many natural methods for controlling algae and keeping pond water clean.

Nutritional imbalance in a pond encourages algae to populate, leading to green pond water. When nitrate and phosphate levels in the water are high, an algal bloom is likely to emerge. To solve this issue, you have to clean your pond, reduce the fish population, and add beneficial plants. 

In this article, we will tackle the issue of having green pond water and how to resolve it. We will also provide steps and tips to prevent your pond water from turning green. With these helpful tips, we guarantee you will restore your pond’s enthusiastic look.


What Causes Green Pond Water?

Green water consists of millions of microscopic algae cells floating in the water. The chloroplasts inside them photosynthesize and convert sunlight into energy, giving them their green color, just like plants.

Spores are often airborne, but any body of water that receives enough light and nutrition can turn green. This is due to open water’s exposure to sunlight in the garden pond. It’ll be most prevalent in warmer weather with extended exposure and a lot of nutrients like nitrates and phosphates from the fish.

However, even when all of the optimal conditions for keeping clear water are there, algae finds a way to persistently cloud a pond. This might be caused by a buildup of organic debris in the pond, a large fish population, or even your water supply.

Because there is a nutritional imbalance in the pond, the algae generate green pond water. An algal bloom generally occurs when nitrate and phosphate levels in the water are high. Many factors cause nitrate and phosphate levels to rise in the first place.

Sludge and filth at the pond’s bottom are some of the culprits. As this layer of organic debris decomposes (dead algae, fish excrement, leaves, grass clippings, etc.), nutrients are released into the water, allowing algae to flourish. As more muck accumulates, more nutrients are released.

Having too many fish in a pond is another major source of algae. Keeping koi or goldfish in a pond is fun, but the excrements they produce break down into nitrates, which algae thrive on. Most people acquire koi while they are young, unaware of how enormous they can grow. A tiny pond with four or five giant koi can create a significant quantity of excrements, producing a nutritional imbalance.

Goldfish, on the other hand, do not grow to be particularly huge but are quite prolific, spawning many times per year. In only two seasons, those who add a few goldfish to their pond are frequently swamped with many generations of goldfish.

The last reason for green pond water is a lack of sufficient plants. Plants consume the same food – nitrates and phosphate – which means pond plants and algae naturally compete. Because there is nothing else to lessen the nitrogen load if you don’t have any plants in your pond, you will almost certainly have an excess of algae.


A pond is a great water feature to add to your backyard. It can provide fresh air, beautiful scenery, and a calming natural sound. But the thing is, ponds are expensive to build and difficult to maintain. If you are still not sure whether you want a pond in your backyard or not, here are 5 benefits of having a backyard pond that may help you make a decision. 


Steps to Clear Your Green Water Pond Naturally

Single-celled, free-floating algae turn your pond water green. It’s one of the most common issues people have with their ponds, and it may be difficult to control at times. Luckily, there are various natural techniques to manage algae and keep pond water clear and green.

However, be mindful that certain ponds appear to be troublesome at all times. Other ponds only require a “fix” at specific periods of the year by providing them with algae-killing and pond water-clearing remedies.

Here are steps to follow to organically clean your pond and establish a more balanced ecology with long-term effects.

Step 1: Clean out your pond and get rid of the sludge

Cleaning the muck and sludge from the bottom of your pond may drastically reduce the number of nutrients that nourish algae. A long-handled net may readily do this in small ponds. If you have a big pond, a pond vacuum is a great way to get rid of sludge quickly and easily.

Doing this a few times over the season, in the spring or mid-summer, and again after the leaves have fallen from the trees, is generally enough. In the fall, using a net to cover the pond will prevent leaves from entering the pond, making upkeep easier. Adding a sludge & muck reducer to the pond is another technique to minimize organic debris.

These muck reducers are made up of all-natural, helpful bacteria and enzymes that devour sludge and convert it into nitrogen gas that floats on the pond’s surface.

Pond skimmers are commonly used by pond hobbyists with bigger ponds. Skimmers help lessen the rate at which you need to clean the bottom of your pond by continuously skimming the surface and preventing leaves and debris from settling to the bottom.

They also simplify filters and pump maintenance. Bottom drains are becoming more popular in ponds because they continuously take trash from the pond’s bottom and deposit it in the filtration system, where it can be readily removed. Bottom drains essentially remove the need to clean or vacuum the pond’s bottom manually.

Step 2: Reduce the amount of fish

Fish, as previously stated, constitute the primary source of nutrients for algae. If your pond’s algae issues are recurring or chronic, it may be time to lower the quantity of fish in your pond.

Although it might be tough to let go of koi or goldfish you’ve owned for a long time, having too many fish can lead to water quality issues, which can result in ill fish or even abrupt die-offs after spawning or in the winter. Give a few fish to pond-owning friends or neighbors. Place an ad in the local newspaper or online to sell or give away your fish.

Try to avoid the urge of buying additional fish once you’ve lowered the amount of fish you have. If your pond just has goldfish, try feeding them less food. Natural food sources for goldfish include algae, worms, and insect larvae, which may be found in most ponds. Your goldfish will still be healthy if you feed them less food but will have fewer offspring.

Step 3: Increase the number of plants

Plants not only fight with algae for nutrients in your pond but also provide shade, a refuge for fish, and contribute to a more natural habitat. The more plants you have, the better, although some plants are better at lowering nutrients than others.

If these ideas didn’t work in your pond, you can use chemicals and other alternatives. Just be mindful when doing so since chemicals have some negative effects on the biodiversity of a pond. Thus, read the instructions and labels of the chemicals before using them.


Tips to Prevent Your Pond Water From Growing Green

A small number of algae can help with the coloration and overall health of your fish. It can also help them blend in with their surroundings and avoid being detected by predators. However, too much green water on a bright illuminated day can release too much oxygen, causing lethal embolisms to your fish.

Since predators can’t see the fish, you can’t either, making it tough to count them and ensure they’re all alive and well. Here are some tips to prevent green pond water.

1. Maintain a Healthy Fish Population

Fish are beautiful creatures and features to have in a backyard pond. However, selecting the ideal fish for your pond is only half the battle. You must pick the proper amount. There are more natural biological processes when there are more fish in the pond. Fish create more fecal material, which provides the necessary nutrients for green water to develop.

Check how many fish are appropriate for the volume of water in your pond. You may avoid an overabundance of waste and minimize the nutrients available to stimulate the formation of green water algae by keeping a reasonable number of fish based on the size of your pond.

2. Avoid Overfeeding Your Fish

If you have a large number of fish and other animals but overfeed them, you’re likely to introduce a lot of waste into your pond. Not just from fish’s normal biological processes, but also from food that isn’t eaten.

In the pond, leftover fish food decomposes into waste, stimulating the development of green water. If your fish aren’t eating all of the food you provide them, cut down the quantity you feed them and make sure there’s nothing left.

This is most likely to happen in your pond during winter, when the fish’s appetite lowers.

3. Provide Some Shade If Possible

Algae that cause green water are plants, and like any other plant, they thrive in the sunlight. Any pond that isn’t shaded will suffer as a result of this. Even though designing a pond with shade isn’t always the best option, there are still methods to get some.

Aquatic plants which float on the surface, such as water lilies, are an excellent technique. They give partial shade, reducing solar exposure for algae and protect fish like Koi, which can get sunburned.

4. Beneficial Use of Bacteria

As previously said, algae are single-celled plant creatures that generate green water. Such organisms usually appear when the levels of nitrates and phosphates in pond water are out of balance (excessive), giving algae the nutrients they need to develop and survive in ideal circumstances. These nutrients are increased by some of the factors stated above but may be reduced by using a good bacteria treatment.

5. Make Sure the Pond Is Well Aerated

Aeration devices can help assist beneficial microorganisms in breaking down and eradicating green water algae by increasing the quantity of oxygen in your pond. They help reduce carbon dioxide emissions by raising oxygen levels. As a result, algae have less nourishment and develop more slowly. Water elements, such as waterfalls, fountains, and even pumps and filters, are excellent aeration devices.

6. Add Beneficial Plants

More nitrates created by fish from feces and food waste can be absorbed if your pond has enough aquatic plants. Since algae depend on nitrates, this leaves very little space for them to eat. Floating plants will help limit algae growth by providing shade and reducing sunlight in the pond. Submerged plants can release oxygen into the water by attaching themselves to a rock.

Lilies and lotus are examples of floating plants, whereas hornwort, parrot’s feather, and anacharis are examples of submerged plants.


Aside from being something nice to look at and listen to, your backyard pond can also be home to numerous living creatures. If you have enough space, you can definitely get a few fishes to live in your pond. Among the numerous fishes that you can keep, which species should you choose? Here are 12 amazing fish you can keep in your backyard pond



When you originally imagined the perfect pond, the last thing you expected was it looking like vegetable soup. Unfortunately, that is the case for many pond caretakers. Green pond water is a typical and reoccurring issue. A pond’s looks, as well as the quality of the water it holds, are both affected by it. The good news is that this article provides suggestions to assist you in avoiding green pond water.

Algae is the main culprit in turning your pond water green. To avoid green pond water, you need to maintain and control the algae population in your pond. The good thing is, there are a lot of natural ways for you to do this. Follow one or a few of the tips that we shared in this article to restore your pond water to what it was before.

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