6 Causes of Cloudy Fish Tank and 5 Ways to Clean It


Why is my aquarium's water cloudy? If you have ever asked this question, you have a problem. But you are not alone. All hobbyists experience cloudy tank water at some point.

The clarity of your aquarium water speaks of the level of your maintenance and care. And in this post, we will share with you the possible causes of a cloudy fish tank. Let us dig deeper into the reasons for the cloudy water in the aquarium.

1. Overfeeding

Overfeeding your aquarium pets will lead to uneaten food, which then becomes a great factor in decomposition. When the decomposition of food takes place inside your water tank, it will give off ammonia and nitrites. Cloudy water is so frustrating for the aquascapers, not only because it appears to be unpleasing, but also because it harms the aquarium pets.


2. Nitrates Due to Overpopulation

Another cause of cloudy tank water is overpopulation or overstocking with too many shrimp, fish, or snails. Their waste, including food waste, is dirtying your aquarium. If you overstock your tank, it will lead to a spike in nitrate levels. And when this happens, it makes the tank water foggy and dirty.

3. Bacterial Bloom

When your filter system is maturing, bacterial bloom happens. But it resolves itself in a matter of weeks or even months. But you can help the good bacteria in the filter by vacuuming the water tank at least once a week to get rid of uneaten food, fish waste, and debris from your plants.

4. Algae Bloom

You might already be aware of algae issues if you have owned an aquarium for a long time. If you are not familiar with algae yet, it is a plant-like organism that grows in your tanks. They can grow on your tank’s sides or sometimes become visible through your aquarium decorations. If it is left unchecked, it will give your entire water tank a greenish hue.

Algae are known to consume what typical aquatic plants love, such as food, sunlight, and nitrogen. If there is too much sunlight and nitrate in the system, it will thrive. However, they make an impact on your tank’s ecosystem just the same way plants and fish do. But an imbalance in the ecosystem brought about by the algae’s spike can harm your fish and shrimp.

5. Gravel Residue

One overlooked mistake could be the dirt from the gravel that is not washed thoroughly. When you notice the dirty tank water, immediately drain it and wash off the gravel until it is clean and clear up a cloudy fish tank before adding your pets and plants.

6. Dissolved Elements

You might be wondering why is my fish tank still cloudy after cleaning it? Well, If the gravel is washed properly but the cloudiness of the water has not changed, then most likely a high level of dissolved substances like phosphates, heavy metals, and silicates are present. There may be a high pH level and alkalinity as well. You can resolve this through water treatment or reverse osmosis.


How to Maintain a Clear Fish Tank

Now that you have learned the common reasons why your tank seems cloudy; we are going to share with you some ways to maintain a clear fish tank. How to clean up a cloudy fish tank? Here are the answers.


1. Change the Water

It is highly recommended to change 20% of your water tank once a week. If you prefer to fill with tap water, add a dechlorinator and let it sit for two days. Then it will reach room temperature and help maintain a settled pH level, which will avoid shocking the fish once it is poured in. Ensure that the new water’s temperature is close to your current tank water’s temperature.


2. Keep Filter Clean

Your sponge filter keeps the tank healthy, so it must be kept up and running. You have to check the filters on a weekly basis to ensure that there are no blockages and clean them as needed. Cleaning its cartridge is easy. Just use a tweezer to remove any tiny blockages and fish waste. However, don’t rinse it off, as it will wash away the good bacteria that helps lower the nitrite and ammonia levels.


3. Decorations

Putting in beautiful decorations to your tank is an awesome idea, yet, they need to be cleaned periodically. Your tank decorations could be a problem, especially when they are made of plastic. 

These props are prone to algae growth. However, natural and organic decorations such as bonsai tree driftwood, river rocks, and live plants do not need to be cleaned as often.

When cleaning the props, rinse them with water and scrub them using a brush intended only for cleaning your aquatic décor. When maintained, this will keep your tank water clean and clear.


4. Scrape the Glass

Algae don’t just grow in the decorations; they also exist and are visible on the sides of the tank. You can easily remove this by scraping the sides on a regular basis with a scraper or a razor blade. Aside from cleaning the inside of the aquarium, it is better to clean the outside of the glass regularly to remove traces of fingerprints and dust.


5. Welcome a Cleanup Crew

You will need the help of these cleanup crews, such as ghost freshwater shrimps, oysters, and ramshorn snails. They will keep your tank community clean and healthy. Here at Aquafy, we offer you lots of cleanup crews that help you create a thriving environment. Again, keep in mind not to overpopulate them, or else this will lead to a foggy tank!


Final Thoughts

Any aquascaper has experienced having cloudy water, whether an expert or not. But instead of becoming agitated at seeing a foggy aquarium, it is best to identify the possible reasons first. Then, search for the best solutions and preventions. This will help you prepare whenever you face such problems again.


The best way to clear up a cloudy fish tank is to do all these from the heart. Keeping your aquarium clean is never a hard task. It gets easier in the long run. Make it an enjoyable habit to keep your water tank clean, pleasing, and healthy.


  • by Jojo bottrill on

    Thank you. Im a newbie at this and this post is very helpful and informative. Theres several things here i haven’t tried yet so i’ll crack on eith that!

  • by Yutian Mai on

    Well done. This is an incredible post and helped me alot!

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