Why Is My Fish Tank Cloudy?

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If you’ve ever asked, “Why is my fish tank cloudy?” you’re not alone.

There is nothing more frustrating than a dirty tank you just cleaned a week ago, killing the vibe of your aquarium.

Beginner or not, identifying the cause of a cloudy tank may not be as easy as you’d like.

You will have to check several factors, which we’ll talk about one by one to help you get to the bottom of things.

What Color Is the Water?

The first thing to determine is the water’s color. Is it more brownish or greenish?


One of the main reasons for brown discoloration is driftwood. It is a popular aquatic decor, but it can also cause trouble.

This brown discoloration usually happens because you did not pre-soak the driftwood before adding it to the fish tank.

Regular changing of water will clear up this issue.


Green water is the hardest to fix out of all the water discolorations. This is because Euglena, an overgrowth of algae, causes green water.

These algae are always there, but they will only multiply if something disturbs the balance in your tank.

There are a lot of possible causes for the disturbance of aquarium balance, such as:

  • Overcrowding of aquatic life
  • High phosphate
  • Too much light, and
  • Excessive nutrients.

The algae not only disrupt the water’s color but also depletes the levels of oxygen at night.

Fortunately, there are a lot of things you can do to solve this issue. You can try more frequent water changes and tweaking the nutrients in the water.

Turning off the lights and moving the tank away from direct sunlight will also help prevent algae overpopulation.

On top of these, we also recommend adding live plants to lower the levels of phosphate, nitrate, and ammonia in the water.

learn why is my fish tank cloudy

Why Is My Fish Tank Cloudy?

There are a number of possible culprits, and even if you know the cause, it will take time and effort to resolve.

Here are the most common reasons why an aquarium gets cloudy:

The Substrate

If you have a newly set up aquarium and the water is murky, you need to check the substrate you are using.

Most substrates are coated with epoxy for freshwater tanks, but you still need to rinse the substrates thoroughly.

On the other hand, marine aquariums tend to be exceedingly dusty if you do not rinse the substrate in smaller batches.

The Water

Another cause of cloudy water is the water itself. Tap water contains nitrates, silicates, phosphates, and heavy metals.

You can use a tap water conditioner to neutralize ammonia, chloramine, and chlorine items or buy packaged aquarium water.

Some prefer using a reverse osmosis filter system, which removes most contaminants from your water supply.

The Nutrients

It’s normal for a fish tank to get cloudy at some point because of too much bacteria.

In fact, it can even occur in set aquariums if there are immediate nutrients changes.

The immediate change in nutrients will boost heterotrophic bacteria growth. These bacteria are responsible for breaking down fish and plant waste.

During the process, these heterotrophs will quickly multiply and cause the cloudy appearance of the water.

If you are starting a new aquarium with no aquatic life yet, you should let the aquarium go through this process naturally.

For established aquariums, there are specific steps you can take to lessen the nutrients in the tank.

You can change the water completely, reduce food, clean your substrate, or add live plants.

5 Ways To Prevent Having a Cloudy Aquarium

Now that we know what causes water discoloration in a fish tank, it is important that we also know how to battle it.

Below are five proven ways to get rid of a cloudy aquarium water appearance for a better fishkeeping experience.

This way, you can finally stop asking, “Why is my fish tank cloudy?”.

1. Maintain Your Fish Tank

The first question to ask if you have cloudy aquarium water is if you are doing proper maintenance.

Most of the issues you will encounter in fishkeeping can be remedied with a simple water change. A water change will bring stability back into your tank.

In some cases, a nutrient spike will cause a cloudy aquarium. Changing the water will get rid of the excess nutrients and restore the aquarium’s balance.

However, one simple water change may not be enough for more serious problems. You need to do regular water changes to restore everything to normal.

2. Regularly Check Your Filtration System

Slacking on proper filter maintenance will result in cloudy aquarium water.

If you fail to maintain your filtration system, it will not operate to the best of its abilities.

Regularly wash your sponges and replace the floss if needed.

You should also replace your filter floss at least twice a month. Also, clean the piping and tubing in your filters.

Upgrading to a chemical filtration system will greatly benefit your aquarium, but it is pretty costly.

3. Clean the Glass

Cleaning the glass both inside and outside is very important.

Remove water stains outside the tank using white vinegar or a Magic Eraser. You can use a razor blade when cleaning the inside of a glass aquarium.

4. Raise the Quality of Light

Bad lighting will give your aquarium a foggy appearance. This concern is more common when you have an LED lighting system because the light is focused.

If you are buying an aquarium with LED lighting, make sure it covers the length of the fish tank.

It is also good to reduce light time to hinder the reproduction of algae.

5. Cycle Your Aquarium

Cycling is important if you have a new aquarium. Lessen your feeding and avoid adding fish until your aquarium is not cloudy anymore.

You can also test your water for nitrite and ammonia levels and change the water to reduce the nutrients.

Cloudy Fish Tank No More!

There are a lot of reasons why a fish tank would be cloudy, but a remedy is always available.

Even better, preventing the problem from occurring in the first place is easier than resolving it. That is why proper maintenance is essential in this hobby.

We hope you apply the tips and tricks we shared and prevent the occurrence of severely cloudy fish tanks.

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