If your aquarium water has suddenly turned the color of pea soup, it means green water has infested your planted tank. This happens due to an unexpected population explosion of tiny floating algae called phytoplankton. Getting rid of green water with large water changes often doesn't work because it replicates rapidly. Because of this, we need to use different techniques to take control of the situation and stop its spread.

In this comprehensive guide, we dive into the issue of green water in the planted aquarium. In addition, there are numerous effective solutions that exist to eliminate green water in your freshwater aquarium.

Let us explain the causes of green water in the fish tank and how it affects the balance of your aquarium's ecosystem. Keep reading to learn how to identify and clear green aquarium water for a healthy, thriving planted tank.

This article will go over:

• What is Green Water?
• Is Green Water Harmful?
• What Causes Green Water?
• How to Get Rid of Green Water
• How to Prevent Green Water
• Final Thoughts on Green Water

What Is Green Water?

Have you ever seen an aquarium or pond with water so green that it was nearly impossible to see through? This is a sign of a green water infestation, also referred to as "pea soup algae."

The rapid multiplication of single-celled planktonic algae causes green water. This type of phytoplankton differs from other types of algae we encounter in the aquarium due to the fact that it's suspended in the water column. Its free-floating nature means it can replicate at an extremely fast pace, making the aquarium water look green. Basically, this free-floating algae takes over water, giving it a green appearance.

Green water is a relatively common issue in aquariums. However, it can be frustrating for aquarists as it obscures the view of the aquarium and its freshwater fish. 

Is Green Water Harmful?

While unsightly, green water is not directly dangerous or harmful to the aquarium ecosystem or its inhabitants. In fact, in controlled amounts, it can be beneficial to your fish and shrimp. Green water naturally occurs in wild, established aquatic ecosystems. Green water contributes to a certain level of murkiness and tint to the water that helps prey species hide from predators.

This free-floating algae can also serve as food for tiny fry and invertebrates. Many breeders purposely create green water cultures because it's a nutrient-rich food source for newly hatched fry. 

In addition, green water also helps combat high nitrate levels in the aquarium. Since algae, like live aquatic plants, is a photosynthetic organism, it feeds off nitrates and reduces toxicity in the aquarium. Similarly, both aquarium plants and green water act as a form of biological filtration, naturally filtering and oxygenating the water. 

Even though green water doesn't directly harm your aquarium ecosystem and its inhabitants, there are still indirect downsides to it.

Most people widely agree that aquarium green water, although natural, is unsightly and lacks aesthetic appeal. Depending on the severity of its spread, it can obscure your view of the aquarium. This can make monitoring the health of your aquarium's ecosystem and inhabitants difficult.

Green water can prevent plants at the bottom of the aquarium from getting enough light. This can lead to nutrient deficiencies and melting leaves.

Like live plants, algae also consumes oxygen and produces carbon dioxide at night in the absence of light. This can cause a depletion of the amount of oxygen in the fish tank, especially in combination with low aeration and a severe case of green water. Low oxygen levels in the aquarium can stress out your fish and shrimp, leading to disease and even death.  

What Causes Green Water? 

Your freshwater tank can experience a green water outbreak if it is exposed to excessive light, an abundance of nutrients in the water column (such as when dosing liquid fertilizer), or a combination of both issues.

It can also happen when there is too much ammonia in a new tank or when you feed the fish too much. Algae is a photosynthetic organism, so it needs both light and nutrients to grow. It can easily overrun an aquarium once these resources become abundantly available.

Scenarios that can cause an aquarium to experience a green water bloom include:

• Keeping the tank outside or next to a window: Excessive light exposure is an easy way to induce an algae bloom. This is why green water in outdoor ponds is a common occurrence.
• Leaving the aquarium light on for too long: Too much light from an artificial or natural source gives algae the ability to multiply quickly.
• Overfeeding the tank: The more food put into the aquarium, the more waste is produced. This waste breaks down into toxic compounds like ammonia and nitrites, which are a food source for the algae to feed off, encouraging its reproduction.
• Overstocking the tank: An excessive amount of fish in an aquarium leads to an excessive amount of waste produced, causing an abundance of nutrients to be available for the algae to encourage its reproduction.
• Not cleaning the aquarium enough: Aquarium maintenance decreases the amount of waste buildup and nitrates in the water, resulting in a reduction of excess nutrients for algae to aid replication.  

How to Get Rid of Green Water

Green water spreads fast, so doing water changes alone won't stop it from reproducing. It's important to utilize alternative methods to manage its rate of reproduction.

To truly eliminate green water, you must address the underlying issues causing it. Generally, this approach tackles problems relating to excessive light exposure, as well as excessive nutrients in the water column.  

Here are 6 strategies that can help get rid of green aquarium water:

When these strategies are combined, you'll maximize your chances of effectively clearing your tank of green water. Keep in mind that it may take a couple of weeks of extra care and regular maintenance to see a difference in your aquarium.

How to Prevent Green Water

After successfully removing green water, remember these best practices to keep it from happening again in the future.

Make sure to address any problems related to excessive light exposure, as well as excessive nutrients in the water column. Managing both of these variables will lead to fewer green water outbreaks.  

Here are 4 ways to prevent green water in your tank:

1. ADD MORE PLANTS: Since live aquarium plants also use photosynthesis to grow, they can compete against algae for light and nutrient resources in the aquarium. Green water should slowly die back as the addition of more plants continues to utilize a majority of the available nutrients. More plants lead to an increase in supplemental oxygen in the aquarium.

Final Thoughts on Green Water

While green water won't directly harm your fish, it can take away from the aesthetic appeal of your aquarium. This article went into what causes it, its impact on an aquarium, and practical solutions on how to remove it. Clearing green aquarium water is a matter of controlling the amount of light and nutrients your tank gets. From UV sterilization to careful choice of plants, it's possible to keep a beautiful and balanced fish tank.

Remember, the time and care you invest in your aquarium will undoubtedly pay off in the form of a vibrant, flourishing aquatic ecosystem. Keep in mind that every obstacle presents an opportunity for growth, learning, and ultimately, a more beautiful and balanced aquatic environment for both your fish and your own enjoyment.

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