How to Fix Cloudy Fish Tank

Discover the reasons behind cloudy fish tanks. From new tank syndrome to overfeeding, I'll guide you through common culprits and offer practical solutions for crystal-clear aquariums. Get ready to dive into the secrets of maintaining pristine aquatic environments!

Article photo for Why is my fish tank cloudy?
Why is my fish tank cloudy?

It was on a sunny day at a quintessential British funfair, amidst the colourful bunting, the merry hum of the carousel, and the delightful aroma of candy floss, that I tried my hand at the hoopla stall.

To my astonishment, I managed to land a hoop on the winning peg and was promptly handed a goldfish in a bag! With eagerness, I set up a new home for my unexpected prize back at my home. Yet, a few days later, I was met with a puzzling sight: my pristine tank had turned murky. I pondered, "Why is my fish tank cloudy?"

If you've had a similar head-scratching moment about your aquarium's unexpected fog, this guide will shed some light. Let's unravel the mysteries behind a cloudy fish tank and explore the solutions.

At a Glance

Section Description
New Tank Syndrome Initial bacteria bloom in a newly set up tank
Overfeeding Excessive food causing waste and bacteria growth
Poor Quality Tap Water Tap water contaminants causing cloudiness
Overcrowding Too many fish causing excessive waste
Inadequate Filtration Insufficient or clogged filters
Decaying Plants or Fish Decomposing organic matter leading to bacteria bloom

New Tank Syndrome

  • Initial bacterial bloom
  • Cycle of setting up new tanks
  • Natural part of the tank's life cycle

Initial Bacterial Bloom

Photo of a bacteria bloom causing cloudy water
Bacteria Blooms are very common for new Fish Tanks

When setting up a new tank, there's a surge of beneficial bacteria. This is the bacteria responsible for breaking down waste products. As they multiply, they can make the water appear milky.

Cycle of Setting Up New Tanks

The term "New Tank Syndrome" refers to the challenges and adjustments that occur in the first few weeks of a new tank's life. During this period, bacterial colonies are establishing, leading to imbalances that can cause cloudy water.

Natural Part of the Tank's Life Cycle

It's crucial to remember that the bacteria bloom is a natural and essential part of the fish tank's life cycle. Without this, the water wouldn't have the necessary bacteria to break down waste products.


photo of some aquarium tropical fish flakes
Little and often is the best way to feed your fish
  • Excessive uneaten food
  • Rotting food releases ammonia
  • Attracts bacteria leading to cloudy water

Excessive Uneaten Food

A common reason for a cloudy fish tank is overfeeding. When food isn't consumed, it sinks to the bottom, starts to decay, and can make the water foggy.

Rotting Food Releases Ammonia

As food rots, it releases ammonia, a toxic compound for fish. This spike in ammonia levels not only risks your fish's health but also creates an environment conducive for bacterial growth.

Attracts Bacteria Leading to Cloudy Water

The uneaten, decaying food becomes a feeding ground for bacteria, leading to rapid bacterial growth and, in turn, cloudy water.

Poor Quality Tap Water

Product Photo:  Interpet Tap Safe
ALWAYS use tap safe when filling up / water changing your aquarium water - this helps remove any nasty chemicals which may be present.
  • Tap water contains minerals and chemicals
  • Water conditioners can help
  • Test and treat water before adding to the tank

Tap Water Contains Minerals and Chemicals

Often, tap water isn't pure. It contains minerals, chemicals, and sometimes microorganisms that can cloud your tank when first added.

Water Conditioners Can Help

Before adding tap water to your fish tank, use a water conditioner. These products neutralize harmful chemicals and can help clear up cloudiness.

Test and Treat Water Before Adding to the Tank

Always test tap water for pH, hardness, ammonia, nitrite, and nitrate levels. If any are out of balance, treat the water before adding it to the tank.


Photo of an overstocked tropical aquarium
More Fish = More Waste.
  • Too many fish produce more waste
  • Insufficient oxygen for all fish
  • Stressed fish are more susceptible to disease

Too Many Fish Produce More Waste

An overcrowded tank means more fish producing waste, which can overwhelm the tank's natural filtration processes, leading to cloudy water.

Insufficient Oxygen for All Fish

Too many fish also mean less oxygen for each one, which can lead to stress and disease.

Stressed Fish Are More Susceptible to Disease

Diseases can spread rapidly in an overcrowded tank. Sick fish might produce more waste, further contributing to the problem of cloudy water.

Inadequate Filtration

Photo of an internal aquarium filter
If your tank is becoming cloudy very quickly - I highly suggest purchasing an external filter box. Internal tank-filters will not have the ability to clean and promote a healthy environment for your fish.
  • Importance of a good filter
  • Cleaning and maintenance
  • Choosing the right filter size

Importance of a Good Filter

Filters play a vital role in keeping water clean and clear. They remove excess food, decaying organic matter, and waste from the water.

Cleaning and Maintenance

A clogged or dirty filter isn't effective. Regularly clean and maintain your filter to ensure it's working efficiently.

Choosing the Right Filter Size

Ensure your filter is the correct size for your tank. An undersized filter can't effectively clean the volume of water in a larger tank.

Decaying Plants or Fish

Photo of a dead plant inside an aquarium
Decaying plants and fish will only add to your troubles. Perform a daily check around your aquarium looking for dead fish / dying plants.
  • Decomposing matter clouds water
  • Regular tank checks
  • Remove dead or dying plants and fish promptly

Decomposing Matter Clouds Water

Dead or dying plants and fish decompose, releasing waste into the water and leading to bacterial growth and cloudy water.

Regular Tank Checks

Regularly inspect your tank for any signs of dying plants or fish. Early detection and removal can prevent many problems.

Remove Dead or Dying Plants and Fish Promptly

Prompt removal of any decaying matter helps maintain water clarity and the overall health of your tank.

Let's Sum Things Up!

A cloudy fish tank can be a cause for concern, but understanding the potential reasons can help you tackle the issue head-on. From the natural bacterial bloom in new tanks to problems like overfeeding, poor quality tap water, overcrowding, inadequate filtration, and decaying matter, there are various causes.

By recognizing and addressing each one, you can maintain a clear, healthy environment for your aquatic pets. So, next time you ask, "Why is my fish tank cloudy?" you'll have the answers at your fingertips. Happy fishkeeping!