How to Clear up A Cloudy Fish Tank

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How to Clear Up a Cloudy Fish Tank

A cloudy aquarium can make it difficult to enjoy your fish tank. In this article, we explore the many reasons why your aquarium may look hazy and how to clear up the murkiness as quickly as possible.

You will first need to pour some tank water into an empty plastic cup or bucket. This will enable you to inspect the water’s color and cloudiness more closely without causing any interference.

1. Particles in the water

If you see specks or particles in your water, it is most likely due to fish waste, excess food or dusty substrate. Small pieces of substrate can float in the water column when you set up a new aquarium or plant your plants. Most of the time, the powder settles by the filter and gets collected by it after a few days. If you still have problems after a week, multiple large water changes may be necessary or thorough cleaning.

Rinse the substrate

Till all silt is gone.

Setting a schedule for aquarium maintenance is a good idea if the aquarium hasn’t been cleaned in awhile. This will allow the water to remain clean and clear. We highly recommend that you use an aquarium siphon to vacuum the substrate and change out the water. For a step by step guide on how to use an aquarium siphon, see this article.

Also, Clean the Filter Once a Month. Your filter is like a garbage can for collecting waste, and when it gets full, it can no longer collect particles from the water. Use a sponge filter to get rid of the accumulation. Remember that the water will remain cloudy for several hours after you have cleaned your tank and filter. This is because the filter needs to get rid of any floating particles.

If you regularly clean your aquarium but still have murky water, it may be caused by the foods you feed. Messy fish foods (typically the kinds that contain very few binders) can turn into dusty fish poop that breaks apart very easily in the water. Instead, try to feed “cleaner” foods – such as live foods or single-ingredient, frozen foods like frozen bloodworms – that will get gobbled up quickly and turn into more cohesive fish waste.

If you keep eartheaters and other bottom feeders, they tend to stir up the substrate as they search for food at the floor of the aquarium. You may need to add mechanical filtration to clear the aquarium of any cloudiness. Mechanical filtration is any type of filtration that physically strains out debris from the water, much like a coffee filter. Mechanical filtration is made possible by the use of sponge, undergravel, and hang-on back filters. If you have a customizable filter, add a prefilter sponge to cover the intake tube, use a coarse sponge pad to catch the larger particles, and get a fine poly pad to trap the smallest particles. Fine poly pads can’t be reused and should always be replaced if they become clogged with gunk. Power heads can be used to improve water circulation and remove any debris from the aquarium.

Finally, water clarifiers can be used for clearing up water that has become cloudy due to debris. These filters contain a chemical or clay that bonds with suspended particles. This causes them to clump together and get caught more easily by the filter or settle to the substrate. The water clarifier sticks to the particles in order to increase their size. This can make cloudiness look worse than it actually is.

2. Bacterial Bloom

If you see the tank water in white cups and it appears almost like milk with very few visible particles, then you could be dealing with a bacteria bloom. If there is too much nutrients in the water but not enough beneficial bacteria, the bacteria colony will quickly reproduce. The water looks like someone has poured milk into it. (For more information on what is beneficial bacteria, read our guide to the aquarium nitrogen cycle.)

Bacterial blooms often occur when cycling a aquarium or if a big group of fish is suddenly added to the tank because there isn’t enough beneficial bacteria to support the ecosystem yet. This can also occur if there is a large amount of beneficial bacteria that has been removed or killed.

It is easy to do nothing. You don’t need to add UV sterilizer or change the water often to clear the haziness. This only makes the bacterial bloom more persistent. Instead, wait one to two weeks, and the water will gradually clear up on its own as the bacteria reestablishes itself again.


3. Green Water

Cloudy water can also be caused by bacteria. If the tank water in your white cup has a green tint (or your aquarium looks like it’s full of pea soup), you’re probably dealing with an algae bloom. Green water is caused by tiny, free-floating algae and is actually very good for raising baby fish. It is a great food source for fry and prevents larger fish from preying on them. It can block light from reaching your plants and prevent you from looking into your aquarium.

Green water is often caused by a combination of too much light and too many nutrients (often coming from excess food, fish waste, and fertilizers). Like bacterial blooms, green water cannot be removed by fine filter floss or giant water changes. Some people suggest doing a large water changing, turning off the aquarium lights, covering the tank with a blanket for 7-10 days and then performing another large water change to get rid of the algae. Green water can survive on very little light so ensure that the aquarium is fully blacked out. Be careful with this method because your plants may suffer from the lack of light. The dead algae can cause ammonia spikes that can harm fish and other green water blooms from excess nutrients.

Instead of using the blackout method, we recommend getting a UV sterilizer. (Green water is fairly easy to treat, so you don’t need to get a very big one.) The UV actually changes the cell structure of the algae so that it can’t reproduce. After sterilization, you can use multiple water changes to get rid of the green water. Soon enough, your water will be clean again.

4. Brown Water

Tannins are an organic compound found in catappa leaves and driftwood. This is why your tank water may have a brownish tint instead of being green or milky-white. Tannins are often used to keep and breed certain fish that prefer blackwater environments, but most people prefer to keep aquariums with crystal clear water.

If you aren’t adding more tannins to your water, manual water changes may be able to slowly remove brown water. If you have a new piece of driftwood, soaking or boiling it can help the tannins leech out more quickly. These methods may not work. You can try chemical filtration, such as activated charcoal in a bag, carbon pads or Seachem Purigen in a hang-on back or canister filter. Activated Carbon can build up tannins and toxins over time, so it must be disposed. Purigen, however, can be reused and can be “refreshed” with bleach to remove any impurities.

5. Cloudy Aquarium Walls

If you don’t see anything in your white cup of tank water, it could be the aquarium walls causing the problem. Make sure the main viewing panels are clean by using an algae scraper to scrub the inside. Then, wipe the tank’s exterior with an aquarium-safe cleaner. Make sure to use an acrylic-safe scraper to avoid micro-scratches. A background aquarium on the outside or inside of your tank can help to reduce glare and blurred vision.

You aren’t sure how often to clean your fish tanks? Our free guide will show you the best water changing schedule for your aquarium.