Get Rid of a Cloudy Fish Tank Once and For All

In Fish Keepingby PaulK

You wake up one day and find your fish tank water is cloudy. Frustrating right?

Why is my fish tank water cloudy and what do I do to get rid of it?

Well, the first thing you need to do is determine what color the cloudy water is. You do this by getting a white container like an empty CLEAN sour cream container and then scoop up some water to half full or something. Then, because it’s white you can see if the water is white or green or just has some particles floating around.

Generally, it’s going to be cloudy for one of these seven reasons…

When you do a water change, clean the filter, or clean the gravel, you upset the balance of the tank ecosystem. When that happens bacteria in the tank will blossom and grow until balance is restored by bacteria growing the filter medium

Causes of water cloudiness:

Bacteria bloom – Also called new tank syndrome. Certain types of bacteria that live on the bottom of your tank feed off the waste material from fish or food or dead organisms. When you have a new fish tank that you’re cycling, the bacteria in your filter has not grown enough to eat the waste going through the filter. That means the bacteria in the tank grows emphatically, known as a bacteria bloom, and makes your water cloudy.

Poor filtration – Your filter is not cycling enough water per hour. It could be that filter size is too small for the tank and you need to upgrade. You also should have three types of filtration: Biological, Mechanical, and Chemical. It could be clogged filters that need to be cleaned. It’s important to clean or replace your filters regularly (except for the bio-media filter).

Overfeeding your Fish – The food you give your fish has high amounts of protein, so overfeeding them causes waste to build up too fast for the filter to handle.

Poor Circulation – If the water isn’t circulating, dead spots can arise where the water is not being filtered. Bacteria feed off of the dead spots causing bacteria bloom.

Overcrowding your Tank – Similar to overfeeding your fish, overcrowding could result in too much waste being produced for the size filter you have.

Poor water parameters – Too much ammonia or nitrites have built up and is causing the in-tank bacteria to bloom. Always check your water quality with a test kit. Ammonia and nitrites should be close to zero or zero.

Green algae from having your tank light on too long – The light for your tank should only be on at the most 8-10 hours per day. Any more and you start to see algae growth.


Make sure the filter is running well. If the filter is clogged you will need to clean it out and/or replace the non-media filters.
In a new tank with no fish, wait it out until bacteria builds in the filter. You can add bacteria treatment to the water. Most of the bacteria that you add will colonize the filter and out compete the bacteria in the tank.

Change 20% of the water every day until the cloudiness goes away.

Use a UV sterilizer. UV sterilizers prevent the bacteria in the water from growing by affecting their reproduction.

If the cloudiness is caused by particulates in the water, use a coagulating agent like Seachem Clarity. It will make the tiny particles clump together so your filter can trap them easier.

Install a floss filter. Floss can be bought at most stores like Walmart. It’s what they use for stuffing pillows. It’s pretty cheap too. Just cut out a piece large enough for your filter and fit it in the filter holder. It would replace the current chemical filter (usually carbon filter)

Water Treatment to Help Clear Up Tank Water

Water decontaminant – Removes chlorine, chloramine, ammonia, and detoxifies nitrite and nitrate. Tap water contains many contaminants including chlorine, ammonia, and metals which are harmful to fish. When you do water changes, add some of this to get rid of the harmful chemicals.

Bacteria Supplement – adds good bacteria to your new tank that feed on the ammonia. It’s a way to speed up the nitrogen cycle and build bacteria in the filter when you are cycling a new tank.

Filters That Will Help Clear Aquarium Water

There are three main types of filters that every fish tank should have. Biological filters that grow bacteria to help absorb ammonia and nitrites. Chemical filters that filter chemicals in the water, and Mechanical filters that filter out the solid wastes in the tank that are most likely causing the cloudiness.

The important filter for cloudiness would then be a mechanical filter.

Filter pads would be the easiest solution since they can be cut down to size and come in many porosity levels. The higher the porosity, the smaller the particulates the filter will catch, but will also clog faster.

Filter socks would be the best solution for clear water, but require frequent maintenance and aren’t designed for many types of filters.

Pillow casing, does a very good job. You have to be careful though not to get any that are bleached or dyed as that can be harmful for your fish.

Open-cell polyether filter foam. The advantage is this can also double as a biological filter.

Quilt batting is 100% polyester. Make sure there are no additives like fire retardants in the material.

Polyester fiberfill, also called filter floss does a fabulous job.

Polyester mesh fabric can be purchased at your local fabric store. There are many different grades and colors available.

Woven plastic filters are not the most effective, but can be used in conjunction with other filters.

Coarse sponges are lower maintenance but don’t do as good a job in clearing the water.

Remember when you first start a new tank and are cycling the tank, water cloudiness is to be expected. Ride it out and let the good bacteria build in the filter system, then the cloudiness should go away.

If cloudiness persists, then try some of the cures above until your water clears up.

Use chemicals as a last resort. is a participant in the Amazon Affiliate Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to

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