How To Clear A Cloudy Saltwater Tank? (Effective Ways)

Image of fish in cloudy fish tank

The first step to clear a cloudy saltwater tank is to figure out the cause of the cloudiness. Cloudiness due to sand and bacterial blooms will clear on its own. For cloudiness due to other causes, you can improve the filtration, use a UV filter, correct the pH, use activated carbon, try frequent water changes, or check the skimmer.

Let’s take a detailed look at this now.

Why Saltwater Aquariums Become Cloudy?

Saltwater aquariums become cloudy because of the following reasons.

Bacterial bloom.

Bacteria play an important role in converting the harmful nitrogenous organic waste in a fish tank into less harmful nitrates.

However, it takes some time for the bacteria to establish a continuous nitrogen cycle.

Till then, the bacteria population can suddenly change in size.

When there is excess nitrogenous waste in the tank, the number of bacteria may drastically increase.

This population explosion is called a bacterial bloom, and it makes the water look cloudy.

Algae bloom.

Excessive nutrients like phosphate and nitrogen in a saltwater aquarium trigger algae growth.

When this happens, it is called an algae bloom.

Algae blooms will turn the water green, red, or brown. It will also make the water cloudy.

You can distinguish between a bacterial bloom and algae bloom by the color of the water.

The aquarium water will be milky in a bacterial bloom, but algae blooms make the water green, brown, or red.


In aquariums with sand as the substrate, sandstorms may occur.

If you direct your water pump towards the sand at the bottom, it will disturb the sand and mix it with the water.

When the sand is stirred up, the fine particles remain in the water for some time. It causes the tank to appear cloudy.

Salt precipitation.

You may already know that salt water has a higher salt concentration than freshwater.

Amongst other salts, it also contains calcium carbonate, which gives the water a cloudy appearance.

When calcium precipitates, it has a milky white appearance. This spreads over the water and makes the tank water look cloudy.


If there are many mature corals in your saltwater tank, they may be responsible for the cloudy water.

Massive spawning of the corals will cause the water to appear cloudy.

Although you may have a filtration system in place, it may not be able to clear the water quickly enough.

The same also happens when many of your fish simultaneously spawn and release masses of eggs into the tank.

Insufficient filtering.

The filtration system in your saltwater aquarium should remove the waste in the water and keep your tank clean.

However, it will operate efficiently only when you clean it at regular intervals.

If you delay cleaning it for too long, the filter can get clogged and dirty.

When the filter does not operate properly, the waste remains in the water and causes discoloration.

Insufficient filtration also becomes a problem if you increase the number of fish and plants in your saltwater tank without compensating for their additional filtration needs.


If you use a protein skimmer in your tank and haven’t set it up properly, it causes microbubbles to appear.

These microbubbles cause turbulence in the water and make it look cloudy.

It’s also be caused by leakage from the skimmer.

In either case, microbubbles form in the tank, and these excessive bubbles make the water appear cloudy.

How Long Does A Saltwater Tank Stay Cloudy?

Saltwater tanks generally take longer than freshwater tanks to clear up. It takes anywhere from a few days to two or even six weeks for clearing up. The exact duration will depend on what is causing the cloudiness.

Bacterial blooms in saltwater tanks occur during the early stages of the cycling process.

It gets triggered by sudden spikes in the ammonia or nitrogen content of the tank.

However, these will usually settle down in a day or two.

If the cloudiness is caused by sand, you will have to wait until the sand settles down and the water becomes clear again.

Similarly, if the cloudiness is due to improper filtration, precipitation, or microbubbles, you should eliminate the cause of the problem for the water to become clear again.

6 Ways To Clear A Cloudy Saltwater Tank

There are several treatment methods to clear a saltwater tank.

You can try the following solutions to clear a cloudy saltwater tank depending on what is causing the problem.

Change the water and clean the tank.

A water change of 20% to 30% makes a significant difference in restoring your tank to its original condition.

It helps prevent bacterial and algae blooms.

Simultaneously, you should also avoid overfeeding fish which leads to more decaying matter.

A little bit of maintenance goes a long way in improving the color of the water.

Regular water change and tank maintenance will also help with color changes caused by the spawning of coral or fish.

Reassess the filtration needs of your tank.

If you have recently added more fish or coral to your tank, you may have to upgrade your filtration system.

A good filtration system should prevent the tank water from turning too cloudy.

Scrub the filter media, tank surfaces, and decorations.

You can use activated Purigen or carbon in your filter to improve its efficiency.

Take care to perform regular and proper maintenance of the filter, and you can control the issue to a great extent.

Add a UV sterilizer.

When frequent water changes don’t seem to help, consider buying a UV sterilizer.

UV radiations will kill the bacteria and microorganisms in the water. By doing so, it will reduce the chance of bacterial blooms.

A UV filter or sterilizer will help to check algae blooms as well.

pH testing and correction.

We already mentioned that the precipitation of salts like calcium carbonate precipitation could cause the water to turn milky.

You can confirm whether this is causing the issue by checking the pH level of the water.

To fix this problem, take appropriate steps to correct the pH level of the water.

Also, take care to eliminate any excess precipitation from the water.

Adjust water pumps and use a micron filter.

If suspended sand particles are responsible for the problem, you can fix it by changing the water pump arrangement.

When water flows freely, the sand bed will dissipate on its own.

You can also use a micron filter to quickly eliminate the cloudiness and give the water a polished and pristine appearance.

Fix your protein skimmer.

Adjusting your protein skimmer will help to avoid microbubbles.

Check whether the protein skimmer is connected properly and if it is positioned in the right place.

It is ideal if you place the skimmer close to where the water enters the sump.

Also, check for any leakage in the skimmer that may be causing the problem.

If required, consider adding a bubble trap in the sump after your protein skimmer.

It will arrest the production of microbubbles and fix the problem.


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