Why is Fish Tank Water Cloudy? How to Clean it?

Nothing can be more annoying when trying to enjoy your aquarium than a cloudy tank. But why did this occur, and what was the reason behind it? Unfortunately, the answer might not be obvious and may depend on a number of factors.

A fish tank can become cloudy due to several reasons such as new tank syndrome, overfeeding, poor water circulation, a dirty filter, an algae bloom, and the introduction of new fish or plants. New tank syndrome occurs because the beneficial bacteria haven’t established themselves in the tank yet while overfeeding leads to excess uneaten food and an increase in ammonia and nitrate levels. Poor water circulation and dirty filters can cause debris and waste buildup, and high levels of nitrates and phosphates can cause algae blooms. Introducing new fish or plants can also temporarily disrupt bacterial colonies and water chemistry. It is crucial to identify the underlying cause to fix the cloudiness in the fish tank.

Aquarium Water Cloudy

Gray or Whiteish Water

Gravel Residue

 If the water becomes murky shortly after filling the tank or within an hour or two, the gravel was probably not thoroughly cleansed. When the water is clean, drain the tank and rinse the gravel. That ought to fix the issue.

Gravel Residue

Dissolved Components

The second most likely reason for hazy water in a newly filled tank, after washing the gravel, is a high concentration of dissolved elements, such as phosphates, silicates, or heavy metals. The pH of the water will probably be high if you test it (alkaline). In these circumstances, conditioning the water will frequently cure the issue. Utilizing RO (Reverse Osmosis) water is another choice that offers numerous advantages in addition to clearing up hazy water. It may be available at your neighborhood fish store, along with RO water-making equipment.

Using Tap Water

The water being used can also result in cloudy water. Things like silicates, nitrates, phosphates, and heavy metals may be present in tap water. As many conditioners will neutralize substances like chlorine and chloramine, ammonia, and heavy metals, make sure you are using one. Additionally, you have the option of buying readymade aquarium water or a reverse osmosis system. Most impurities in your tap water supply can be eliminated with the aid of RO filters.

Use of Tap Water

Nitrogen Converting Bacteria

It is usual for the aquarium to grow foggy when starting a new one. This is brought on by the colonization of helpful bacteria that oxidize ammonia and nitrites. If there is a significant increase in nutrients, this bacteria bloom might even happen in an aquarium that has already been created.

Heterotrophic bacteria expand as a result of the additional nutrients. These microorganisms convert unconsumed food, rotting plant matter, and fish waste into ammonia. Additionally, they produce a slimy bio coating that forms on the aquarium’s ornaments and walls.

Because of the heterotrophs’ rapid population expansion, the water may become murky. Allow the aquarium to go through this cycle naturally if it is a brand-new setup without any aquatic life. Reducing the amount of food, performing a water change, and cleaning your substrate will all assist to lessen the nutritional levels in an established aquarium. Lowering nutrient levels can also be aided by the inclusion of living plants.

Green Water

Green water is obvious. A bloom of algae is to blame. The difficult part is getting rid of it, but if you know the source, treatment is simpler. These are the main reasons why water becomes green:

Green Water

Too much light

Too much light is the most obvious cause and the simplest remedy. Algae will grow if the aquarium is placed in direct sunlight or the lights are left on for an extended period of time. Reduce the length of time the lights are on, and relocate the aquarium so it is not directly in the path of the sun.


Nitrate levels in aquariums naturally grow over time as a result of fish waste. The only method to get rid of them is to change the water. Make sure your filter is clean and suitable for the size of your tank. Also, make sure you haven’t overstocked your aquarium, otherwise, you’ll be fighting growing nitrate levels all the time.


Phosphates come from two sources: the water itself and items that are in the process of degrading, including fish food. If your water supply is problematic, you may find out by testing the phosphate content of your drinking water. You must treat your water with RO water or a phosphate remover if it naturally contains a large amount of phosphate. moving to a lower-in and cutting back on the amount of food you give your fish.

Brown Water

Brown water undoubtedly detracts from the attractiveness of your aquatic life and may have been unintentionally brought on by the addition of driftwood, a common aquatic ornament.

brown water

If the driftwood was not presoaked before being added to the tank, it may give the aquarium a faint brown tint. The release of tannic acid is the cause of this hue. Regular water changes will help to clear this up, and utilizing chemical filtration, such as carbon, will help the water become clearer. You should test your pH level if driftwood has been added and you notice some brown hue since tannic acids can drop pH.

How to get rid of Algae?

Owning a fish tank will inevitably result in algae. You can prevent algae in a fish tank from becoming a problem for your fish by making the necessary plans and preparations.

Here are a few ways to avoid algae in your fish tank:

Taking Care of your Tank’s Water

Make sure to evaluate the amounts of various substances in water at least once a week, paying close attention to pH levels. Invest in specialized processes that will remove extra nutrients from the water if you notice a trend toward them increasing.

Erythromycin can be used to promote the growth of blue-green algae, but you must carefully follow the usage recommendations because it can harm the beneficial bacteria that are already present in your aquarium.

Stop Overfeeding your Fish

Don’t feed your fish so much food that it floats to the bottom of the tank; instead, learn to estimate how much they will consume in a short period of time. It could be a good idea to put them on a feed/fast schedule where they skip meals one or more days per week.

Bloating and overfeeding

It’s difficult to starve a fish, and by reducing waste in its tank, you are giving them a healthier environment. So don’t think of this as being cruel.

Turn off Aquarium Lights

Make sure your lights are on for a whole 12 hours a day if you have a planted aquarium. However, if you have plastic plants, limiting the amount of time the lights are on is an excellent approach to prevent the spread of algae. Keep in mind that photosynthesis is how algae produce their own food. They, therefore, require light to survive, just like plants do. They can’t be as numerous if you restrict the light.

Turn off Aquarium Lights

Of course, much like humans, fish require a day/night cycle to remain healthy. However, unlike the fish in your tank, most tropical fish do not have a bright light shining down on them in the wild. They can roughly compare the low daylight to what they would see in their home country’s rivers and lakes.

Avoid Natural Sunlight

It is practically little you can do at this point if you have a huge tank and you have already made the error of placing it in direct sunlight. However, if you have a tank that you can move or if you haven’t yet set it up, think about positioning it where the sun won’t be shining on it for a portion of the day.

Avoid Natural Sunlight

It is clear why this is significant: Given enough sunlight, algae will grow like crazy, just like plants do. This can be prevented by following the above instructions and not giving the required food, but why give the algae any food at all?

Additionally, direct sunlight is not ideal for your fish. They could experience extreme stress from the harsh light and the higher temperatures in the tank, which could harm their health. If at all possible, stay out of the sun to protect your fish, tank, and yourself.

Knowing your Water and Performing Water Changes

Check your water supply. If it contains a lot of phosphates, you might want to use phosphate-removing chemicals from your local aquarium store or look for another water source, like filtered water. Testing for nitrate is also advisable because some water sources have high nitrate concentrations. If you are feeding nutrients back into the tank using tap water, changing the water won’t help much.

Changes Water Quality

The most crucial step in preventing algae is to do routine water changes. To reduce the number of nutrients in the water, change 10 to 15 percent of the aquarium water each week. This will get rid of the nitrate, one of the key nutrients for plants, that builds up in aquariums.

Related Post: Corner Fish Tank

Use live plants in your Aquarium

Growing natural plants in your aquarium can significantly reduce the formation of algae. One explanation is simple: Algae and plants compete for the same food sources.

Fish waste is undesirable if you want to halt the formation of algae, but it can be helpful (to a point) if you want to grow live plants. Algae will suffer as healthy plants are better able to absorb nutrients.

Growing Live Plants

Some claim that specific plants emit organic compounds that inhibit the growth of algae. This makes sense because algae can build up on plants, which is obviously bad for the plant.

Although maintained properly, planted aquariums can be ideal miniature ecosystems that serve the needs of both fish and plants. Algal growth won’t be significant when the equilibrium is ideal.

Proper Filtration Maintenance

Fish tank water might become hazy if you neglect filter maintenance. Your mechanical filtration isn’t working to its full potential. Replace your filter floss and clean your sponges by getting into the filters. Filter floss needs to be replaced every other week. Make sure to thoroughly rinse out all of the filter media with tank water. You run the danger of wiping off those helpful bacterial colonies if you use tap water or RO water.

Power filter piping and canister filter tubing should both be cleaned. If you have mechanical filtration, you might want to consider getting a new set. Even though it is pricey, changing to a premium chemical filter media like chemo-pure occasionally helps. All of this upkeep pays off since your filters will work at their peak efficiency, maintaining crystal-clear tank water.

Handling Algae

You are experiencing an algal bloom if your tank water suddenly turns green and hazy. Algae don’t simply grow on surfaces; they also live in the water, so any change in the conditions that let them thrive can result in an abrupt increase in algae growth. This sounds much worse than it actually is, and the answer is usually straightforward.

Green Water

First off, something went wrong with the above-mentioned management measures if you experienced an algal bloom. A rapid increase in waste chemicals in the water is typically to blame. You need to determine why that occurred. Did you eat too much? Have you added any new fish? Have you been skipping certain water changes?

Removing some of the nutrients that the algae are absorbing by replacing the water and adding fresh, clean water is a straightforward remedy. Think of making a second water change for the week at intervals of a few days. After that, go back to your normal maintenance regimen for algae.

Is a cloudy fish tank bad for fish?

No, Cloudy water in a Fish Tank is generally not harmful to your fish.

The Bottom Line on Why is Fish Tank Water Cloudy?

Although foggy aquarium water is an indication of imbalance and may indicate a bigger issue, it is not harmful to fish. When you notice hazy water, the first thing you should do is test the water in your aquarium to determine its quality. Find out your baseline nutritional levels and take appropriate action. A water change will typically assist in restoring the balance.

Filters may make foggy water clear. If your tank is brand-new, your filtration system must catch up in order to maintain tank balance. If your tank is fully packed, you might not have enough filtration and want an additional filter to clear the hazy water. Sometimes the issue is with the filter itself since it has to be. Happy fishkeeping!

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