Why is My Fish Tank Cloudy: Top 10 Reasons

Goldfish on a fishtank
Image via Unsplash

Any gorgeous fish tank can turn into a nightmare when the water develops a mysterious, cloudy consistency. For many fish owners, seeing their tank’s water change from clear to murky white or brown can be incredibly frustrating, as there are many possible causes.

So, how many different causes could there be for a murky fish tank? Well, research shows that there are ten common reasons a fish tank may become cloudy. 

Once you’ve diagnosed the cause or causes, you can find a solution! Depending on the cause of your water problems, the answer could be as simple as adding more water to your tank. Instead of wondering, “Why is my fish tank cloudy?”, know why and get it back to pristine condition today.

What Are the Signs of a Cloudy Fish Tank?

A cloudy fish tank will have water that appears white, gray, or green. You will not be able to see objects or fish clearly or correctly. 

Cloudy fish tanks may also produce a pungent scent, due to an excess of phosphorus in the water. If your tank’s water is not clear and easy to peer through, you have a cloudy fish tank.

What Are the Dangers of a Cloudy Fish Tank?

Cloudy fish tanks are a symptom of unclean, unfiltered water. Because fish live and breathe in the water in your tank, they are dependent on that water’s clarity and cleanness and free from harmful chemicals, particles, and elements.

A cloudy fish tank can not only make your aquarium unattractive, but it can prove potentially fatal to your fish. Figuring out why your fish tank is cloudy is the first step to saving your fish from illness, stress, and death.

What Are the Dangers of a Cloudy Fish Tank

Why Is My Fish Tank Cloudy?

1. Gravel Residue

If you’ve recently purchased a tank and set it up, you may notice that a cloud of whitish or gray “powder” seems to float upwards from the bottom of your tank.

If you’re using gravel as the base of your tank, you’re likely to deal with “gravel residue” immediately after installation. 

The powdery particles that cover the gravel loosen themselves and are filtered out of the tank via your mechanical filter. Should you let this residue settle back onto the gravel, you will continue to see problems with clarity of your water.

If you’d like to avoid the situation altogether, wash your gravel before filling your tank. Just rinse the gravel in a large container – you can even use your empty tank – and run water through it and across it until the water begins to run clear. Then cover the clean gravel with clean, clear water.

2. Dissolved Particulates

Unlike the particulates that rise from unwashed gravel, suspended particulates in your tank water may come from a poor-quality tap or groundwater that is heavy in dissolved phosphates, nitrates, heavy metals, or silicates.

Not only is this water not very good to drink, but it’s also not suitable for your fish or your tank’s water clarity.

You can purchase a conditioner to use in your water, and that can help correct pH issues related to dissolved particulates.

Having a high-quality water filter can also help, but perhaps the best solution to water that is dense with suspended particulates is a reverse osmosis machine.

To have the most transparent and clean water possible, it is always best to use filtered water, and using reverse osmosis is one of the most efficient ways to turn cloudy water transparent.

3. Bacteria

If you set up your tank a short while ago and are now wondering, “Why is my fish tank cloudy? My gravel is clean, and the water I used was clean and clear!” you may be dealing with a bacterial bloom.

Good bacteria, strains that will clean the water and keep it clear, take many months to develop, and in the meantime aquatic plants may die and begin to rot, or excess decaying food may sift down to the bottom of the tank.

The excess number of bacteria that is organically generated by these decaying processes can make your water cloudy and dark.

Correct feeding and removal of rotting plants can solve this problem nearly instantly but having an active filter will also help.

4. Algae Growth

Is the water in your fish tank green? The culprit is algae. While seeing algae growing is usually considered a good sign, as it means living things can survive in your tank without too much intervention.

However, when it starts turning your tank green, spreading over the glass, or causing breathing issues for your fish, it is time to get rid of it. 

There are a few causes of algae spread through your tank. Too much sunlight can cause algae to reproduce, and the presence of too many nutrients, including phosphorus and nitrates, can feed algae too much and cause it to take over.

Monitoring your tank’s pH and nutrient levels are crucial to keeping algae levels under control.

Algae Growth

5. Overpopulation

When there are too many fish inside of your tank, things go downhill quickly. Not only do your fish become stressed from the cramped environment, but the reservoir also fills with detritus in the form of dead skin, decaying plants, rotting feces, and dead fish.

Cleaning and removing these wastes can be nearly impossible with an overpopulated tank, and maintenance is likely to be constant. Ensure that you are not keeping too many fish in your tank, and you may immediately see improvements in the water quality!

6. Overfeeding

Though it may seem wise to feed your fish every day, in most cases, it is unnecessary and only leads to murky water. Any food that is ignored by your fish ends up becoming a rotting mess at the bottom of the tank.

Most fish are perfectly healthy when fed once every two or three days. Although it is vital to research your species’ specific needs, it also essential to keep in mind that fish do not eat as often and as much as terrestrial pets and animals.

The more you overfeed your fish, the more work you will need to put into keeping your tank clean.

7. Improper Water Changes

Frequent water changes are a must for any tank. Removing approximately 10% of the water in your tank and replacing it with clean water every week is the proper way to keep your water clear.

Small, frequent water changes will ensure that you’re not disrupting the beneficial bacterial base while keeping rotting plant matter and uneaten food from spoiling your tank’s water quality.

8. Chemical Reactions

When adding various chemicals to the water in your tank, it is essential to remember that chemicals react. If you notice that the water in your tank had become cloudy after applying chemicals, be sure to test the chemicals used in separate glasses of water to determine which one is causing the cloudiness.

Limiting the use of chemicals is also a great way to limit the amount of cloudiness caused by them, and with the full range of natural amendments and filtration systems available today, it has never been easier to keep a clean and bright fish tank free of synthetic or excess chemicals.

9. Faulty Filter

Proper filter maintenance can help tremendously in keeping your tank clean and bright. With a high-quality filter and regular cleaning of that filter, you’ll never have to wonder “Why is my fish tank cloudy?” ever again!

Typically, there are three types of filters available to fish tank owners:

  • Biological – Bacteria, microorganisms, plants and fungi that naturally filter waste and toxins from the water.
  • Mechanical – Physical filtration using an automatic device that takes in water, pushes it through a filter, and expels it back into the tank, clean and bright.
  • Chemical – Chemical filtration comes in the form of charcoal filters placed inside the tank. The charcoal acts to filter out toxins in the water, but it must be changed often.

The best filtration system is one that combines all three types, with biological methods far outweighing chemical means of filtration.

10. Wooden Decorations

Wooden decorations can do wonders in a fish tank. They can lower the water’s pH, boost the immune systems of your fish, reduce stress, improve appetite, and even encourage mating! 

Wooden decorations do this by naturally releasing tannin, a chemical that can turn your clear water a soft yellowish or brownish color.

While the coloration might not be the most pleasing, your fish will love the benefits of the tannin, so the choice of whether to use wooden decorations is up to your preferences.

A cloudy tanky is bad news. To ensure it doesn’t happen, you have to properly balance the tank’s water in terms of pH, nutrients, etc. Here’s an idea of how to achieve that “perfect balance” in your fish tank or aquarium… 

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