How to Keep Aquarium Water Clear

Three Methods:Setting Up Your AquariumMaintaining Your AquariumTroubleshooting Cloudy Water

An aquarium with clear water is a sign of a healthy environment. Fish need clean and healthy water in order to thrive and live. Uneaten food, fish waste, and plant debris raise the pH level of the tank and make it unsafe. There are a number of ways for you to keep your aquarium water clear.

Method 1
Setting Up Your Aquarium

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    Leave the cloudy water. Many times cloudy water will disappear on its own while the water environment adjusts. Often, cloudy water is a result of mixture of microscopic organisms, such as bacteria, protozoa, and micrometazoa.[1] These organisms come from your fish, the food, and waste. Usually, the tank will balanced out and clear up within around a week.
    • Be patient. Before adding chemicals or trying to do anything drastic to fix the cloudy water, remember that the aquarium is full of living organisms. Figure out why the water might have become cloudy before doing anything to the water. Adding unnecessary chemicals and cleaners can upset your tank environment and harm your fish.[2]
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    Add in good bacteria. Adding in good bacteria helps the natural processes of the tank. You can get good bacteria in the tank in a couple of ways. You can buy prepackaged bacteria from the store or buy gravel that has the bacteria already on it. You can also add gravel, rocks, driftwood, or a filter pad from an established tank to your own tank. It will have the bacteria on it.[3]
    • Bacteria cultures will help to eliminate ammonia and nitrite, which are toxins. It changes them into less harmful nitrate, which is then removed during water changes.[4] The best bacterial species to do so are Nitrosomonas and Nitrobacter.[5]
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    Place suitable live plants in the tank. Another way you can help keep your tank clean is by adding live plants. Live plants are covered in good bacteria, and they also are a filter for the water.[6] You can buy these at your local pet store.
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    Determine if you have the correct filter. There are different filters that do different things for your fish. Cloudy water might be due to having the wrong filter. The filter you choose depends on the density of fish, the type of aquarium you have, and the use of live plants or artificial plants.
    • There are three different filters to choose from. Mechanical filters remove the particles by forcing the water through a material that catches the particles. Biological filters use bacteria to change toxins into less toxic substances. Chemical filters use chemicals to remove toxins or chemical from the water.
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    Stock your tank thoughtfully. When you are putting fish in the tank, don’t place too many in it. This can cause health problems and make your tank harder to clean.[7] Try to keep the amount of fish around one inch of fish per gallon of water.[8]

Method 2
Maintaining Your Aquarium

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    Change the water. A good rule of thumb is to change 20% of the water in the tank every week. If you use tap water, let it sit for two days. This allows it to reach room temperature plus allow the chlorine in it to dissipate, which helps the water not shock the fish when it is poured into the tank.[9]
    • You can also buy a device that hooks to your faucet that vacuums the gravel while removing and replacing water. You don’t have to wait a few days if doing it this way. Just make sure you make sure the temperature is close to your tank’s temperature and that you add in a chlorine remover.[10]
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    Keep your filter clean. You must keep your filter up and running. The filter helps keep your tank healthy and prosperous, so not changing it or neglecting it can lead to cloudy water or even fish death. Read the instructions for your filter to know how to take care of it.[11]
    • All filters need to be examined monthly and changed if needed.[12] Check them weekly for any blockages or build up. Clean or replace as needed.
    • Read the instruction manual that came with your pump to make certain it is properly installed and working as it should. The pump is important in aerating the aquarium with oxygen from the air. If it is not working properly the fish will suffer especially if the water is cloudy from waste matter.
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    Clean your aquarium. Another way to try to clear up your water is to clean your tank regularly. You should set up a schedule to clean the tank at least once a month. This is in addition to the regularly scheduled water changing you should be doing at least once a week.[13]

Method 3
Troubleshooting Cloudy Water

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    Look for bacteria bloom. After changes to your fish tank, such as a large water change, a thorough cleaning, or medicating your fish, a bacteria bloom can occur. If this describes what led to the cloudiness in your tank, then be patient. The bacteria will balance out in a few days, and the water should clear on its own.[14]
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    Check your filters. If your filters are not working properly, then the water can become cloudy. There is bacteria in your filtration system that consumes byproducts like ammonia and keeps things clean. If the filters stop working, the bacteria can build up in the water, making it look cloudy.[15]
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    Adjust for additional fish. If you had recently added new fish to your aquarium, make sure the tank set up can handle the additional fish. For example, if you just added a larger fish to a tank that had smaller fish, it might be too much for the filtration system. Add a different filtration system, or lessen the amount of fish in your tank.[16]
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    Refrain from overfeeding your fish. Overfeeding your fish can cause cloudiness in the water. Fish need to be fed sparingly. Feed them a light amount of food once a day, and give them one or two fast days a week.[17]
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    Be mindful with decorations. Sometimes, cloudiness can be caused by decorations. Make sure to wash all decorations carefully before adding them to the tank. Check all decorations in your tank to make sure they are designed for aquariums and purchased at good pet stores.[18]
    • Check for melting or misshapen decorations, softening or loosening decorations, or flaking paint or discolorations on decorations.
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    Control algae. Green algae clings to the sides of the tanks and sometimes to the decorative items in the tank. A good time to scrape algae from the sides is when you change the water. Use a soft plastic squeegee to gently scrape the side, then rinse under water to clean before taking another swipe. Remove all the ornaments and scrub under clean, running tap water.[19]
    • Make sure your tank doesn’t get too much light because that can cause algae growth. Don’t place your tank close to a window and only keep lights on for 10 to 12 hours a day.[20]
    • It is important not to overfeed your fish as leftover food can contribute to algae growth.


  • Most of the time, cloudy water will clear up on its own. Just be patient.
  • Do not overstock your fish tank or you will have a difficult time keeping it clean.
  • Make sure to set up your aquarium’s filters and pumps according to manufacturer’s direction.
  • A thorough cleaning of your tank—gravel, filters, décor, tank—along with draining all the water may be needed. But only attempt this after you have tried everything else.

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Categories: Aquariums