Aquarium Cleaning – Handling Cloudy Aquarium Problems

Nearly every fish owner has had to deal with cloudy or hazy water. It can be a problem that is hard to troubleshoot and create an action plan, especially if water changes do not seem to solve the problem. Cloudy aquarium water causes are often not crystal clear but by examining the situations around the time of the clouding and the color of the water, the cause and treatment for a cloudy aquarium can be narrowed down to a few common causes of this pet owner problem. Most cloudy water cases can be eliminated simply by changing tank maintenance procedures and making sure the gravel is clean, using high-quality fish food and doing weekly 10-15% water changes. These three things combined can often resolve most aquarium water problems.

Green Water is always caused by algae.

Green water and algae blooms are hard to get rid of if you don’t know what is causing the algae growth. By knowing the cause of the algae overgrowth, you’ll be able to tackle it and have an easier time clearing the tank.

Too much light is overlooked and the most common cause of algae growth. Algae require light to grow so if your aquarium has been in direct sunlight at any point of the day or the lighting was left on too long, you’ve created the perfect environment to foster an algae bloom. You may not even realize that the sunlight shines on your aquarium while you’re at work each day. To eliminate excess light, move the aquarium carefully and properly or reduce the amount of lighting the aquarium gets each day so your fish enjoy the more sometimes more shadowy and underwater lighting they and their environment enjoys the most.

Excess nutrients such as phosphates and nitrates will also be reduced as they encourage algae growth. It’s important to deal with phosphates and nitrates but a water change will help to start the process of clarifying your tank and improving the water quality.

Phosphates can lead to algae and come from detritus and biologically decaying materials such as leftover fish food and can be from the water source directly. Phosphates in tap water can remain even if the water is dechlorinated as the phosphates remain to feed algae. You can test your tap water for phosphates. To prevent green water in an aquarium filled with tap water with phosphates, using RO (Reverse Osmosis) water. Your local fish shop may sell it or sell filtering units capable of making RO water. RO water or phosphate removers to treat the water will eliminate the substance. You can also switch to a lower-phosphate fish food or reduce the amount of food you feed your fish. Fish should only be given enough food they can eat in a couple of minutes or the tank will become a biohazard.

Nitrates occur as part of having fish. Nitrates are the result of fish wastes. Your fish not only live in their aquarium but also use it as their cafeteria and toilet. A water change can reduce nitrates if done in 20% weekly changes, but filter care and size can prevent a necessary emergency 50% water change. Having a filter large enough to keep the tank clean and filter waste will keep nitrates at a minimum and the more fish and stocked your aquarium is, the more nitrates will be produced. If you have an aquarium with overcrowding, you will have nitrates and more fish waste to contribute to the algae bloom.


White, hazy, or greyish water can be caused by something as simple as gravel residue.

If an aquarium is cloudy after filling or within a few hours, the gravel was not properly washed and rinsed before being added to the new aquarium. This occurs often in new aquarium setups. Always properly wash your gravel before adding it to a tank, even if adding some as décor in a contrasting color to an established tank. Draining the newly set up tank and properly rinsing the gravel multiple times until the water is clear should resolve this cause of If the water is cloudy immediately or within an hour or two of filling the tank, it’s probably due to insufficiently washed gravel. Drain the tank and rinse the gravel until the water runs clear. That should resolve the problem.

Dissolved materials also can cause cloudy water in a newly filled tank. Water testing can reveal the presence of dissolved constituents such as silicates, heavy metals, or phosphates. Water in this state is usually alkaline when the pH is tested, Conditioning the water can remove the particulates and clear it.

Gradual onsets of cloudy water in an established tank is usually caused by too much good bacteria. An aquarium will normally because a bit lazy or cloudy as the tank cycles and the healthy necessary bacterial colonies that are part of any aquarium are getting established. It can take weeks or months for those tank cleaning bacterial to get working on cleaning the water, so the milky water is a temporary thing usually. Once cycled, the water will clear itself. Bacterial blooms are a normal part of aquarium keeping and are only a concern if they do not resolve after a couple of months. Removing decaying plants, excess food, and partial regular water changes can usually clear bacterial overgrowth up. Just be sure to vacuum the gravel and cut back on food if there are too many food particles found in the tank. It there is more debris than can be vacuumed from the tank by vacuuming the gravel and water changes, a flocculant is required. These are known as “water clarifiers” and cause particulates to clump into pieces so they can be removed by the filter, which should be cleaned, and the cartridges replaced.

Here’s wishing you clear tanks ahead and happy fish!




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