How To Stop Cloudy Water In Fish Tanks?

By Harry RamosLast update: 2024-06-13
How To Stop Cloudy Water In Fish Tanks?

“How to stop cloudy water in a fish tank?” – this might be the most popular question of aquarium owners. For starter aquarists, you might be confused and wonder what it means, why it happens, and if it causes harm to their fish.

A good thing is that cloudy water is just a sign of bacteria blooming because of different reasons, and it isn’t a serious case.

As stated, there are a lot of reasons for bacteria blooming, each of which requires a specific solution so I’m going to mention one-by-one for you to fix this issue optimally.

How To Stop Cloudy Water In Fish Tanks

Green Water

This issue is a no-brainer.

It happens based on algae bloom. To eliminate green water, you should understand what is exactly the reason. Here are some common causes of green water in your fish tank:


The raise of nitrates in your water tank is just a byproduct of fish wastes. So, if you keep the water frequently changing by using a good filter, this issue will happen no more.

How to choose “a good filter”?

How To Stop Cloudy Water In Fish Tanks?

Good question! A good filter should remove fish wastes well and is adequate for the aquarium size.


There are two primary sources causing phosphate level to be high in the water:

  • Water source
  • Decaying matter (for example fish food)

First thing first, you should test your tap water for phosphates. If its phosphate level is under 0.15 ppm, algae can’t bloom, which also means the reason for the high phosphate level is decaying matter.

How To Stop Cloudy Water In Fish Tanks?

In this case, reduce the amount of fish food given to your fish or change the food brand.

But if you find the phosphate level in your tap water is 0.15 ppm, utilize a phosphate remover or RO water to treat the water.

Too much light

How To Stop Cloudy Water In Fish Tanks?

This is the most popular reason causing green water and it’s also the easiest. Like other plants, algae bloom only happens if it receives enough sunlight or light exposure.

To fix this matter, just move your aquarium tank to a new place where there’s little to no direct sunlight. Or cut off as much time of lighting as possible.

Grayish Or White Water

Insufficiently washed gravels

How To Stop Cloudy Water In Fish Tanks?

This commonly happens with novice aquarists. If after filling your fish tank with the water and you find cloudy water happens instantly or one hour, it is because of the gravel residue.

What you should do is drain the aquarium and clean thoroughly the gravel until the water runs clear.

Bacterial blossom

A couple of days, weeks, or even months after you set up a fish tank, if you find a milky white cloudy color to the water, it is bacterial bloom.

Don’t worry, it is a common issue that happened in new aquariums going through the first break-in stage, made by beneficial bacteria floating free in the water.

The good news is it isn’t harmful to your fish, shrimp, or snail but just make your tank seem to be dirty and eye-sore. If you’re a patient aquarist, just wait a few weeks or months for this cloudiness to go away once they have settled down.

Another reason causing bacterial blossom is excess uneaten fish food or decaying plants.

The best solution for this case is cleaning your aquarium frequently; removing uneaten fish food or reducing the amount of food fed each time and cleaning up decaying plants.

If the bottom of your fish tank is covered by gravel, don’t forget to vacuum them often.

Besides, performing partial water changes is another efficient way.

While cleaning an aquarium, there might be some uneaten food pieces or debris particles that are hard to remove; you can use a flocculant. This substance will clump debris particles, fish wastes, and uneaten food pieces together to be cleaned up more easily.

Find the flocculant in any fish shop

Dissolved constituents

If the water in your aquarium isn’t clear at all after cleaning the gravel, consider the reason might be from a high volume of dissolved constituents, like heavy metals, silicates, or phosphates.

How To Stop Cloudy Water In Fish Tanks?

In this case, test the water.

If the pH keeps at high levels, it means the water contains too much alkaline. Treat it with specialized conditioners or use reverse osmosis (RO) which is commonly sold in any fish shop.

Or, you can buy a unit that can make RO water.


How Long Does It Take For Cloudy Aquarium Water To Clear?

While cloudy water is caused by many reasons, once solved properly, it usually takes around one or two days for your aquarium to be clear again.

Will a filter clear cloudy water?

No, it will not. If cloudy water is caused by free-floating beneficial bacteria and you use a filter to get rid of them, that’s no good for your aquarium in general. Talking about the filter when it deals with cloudy water, the big thing is never to mess with it.

What does bacterial bloom look like?

High concentrations of beneficial bacteria in an aquarium frequently result in cloudy water. It is similar to an algae bloom, which makes the water clarity level is hugely decreased, however, you can’t find a certain visible floating particle in the water.


I’ve just mentioned in detail all the reasons that might cause cloudy water in aquariums, along with specific, efficient solutions. Hopefully, through this post, you’ll know a thing or two about how to stop cloudy water in a fish tank.

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