Why Is My Fish Tank Cloudy & How To Fix It | Aquascape Addiction

Why Is My Fish Tank Cloudy & How To Fix It

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We answer the common question "Why Is My Fish Tank Cloudy" with 5 helpful ways to fix your cloudy aquarium water.

Why Is My Fish Tank Cloudy &  How To Fix It

Having an aquarium is a really fun hobby to have, and even better is how beautiful an aquarium looks anywhere in your home, but what about those times when it does not look so nice? What we are referring to is a problem that many new aquarium owners and new fish tanks experience and that is the problem of a cloudy fish tank.

You may have noticed it or you may have missed it, but what often happens is that you get a new aquarium and wake up the next day to find a foggy and murky fish tank. It can be a real shock to wake up in the morning or come back from work to find that your tank looks like a fog infested seaside fishing town, such a shock that you try to find some kind of quick fix while wondering why is my fish tank cloudy?

You may have tried adding some special solutions recommended by your local pet store, people who are undoubtedly just trying to sell you their most expensive item. Maybe you heard that changing the water and washing out the filter would help get rid of the cloudiness.

Of course these things may be able to solve the problem for a day or two, but what should you do when the problem comes back a couple days later, and trust us, often the cloudy water problem does come back. Before we get right into solving the problem of the murky fish tank, let’s talk about what actually causes the problem.

Why Is My Fish Tank Cloudy?

Many people refer to a cloudy fish tank as “new tank syndrome”, because it is a problem that most often occurs within the first week of buying a new fish tank. Many times this is a problem that only lasts a few days, but sometimes it can also last for a long time.

There are extreme cases where the water just keeps getting foggier until you can’t see anything at all, which is of course not good. You may be wondering, what actually causes your fish tank to become cloudy.

Well, the reason that your aquarium is fogging up is due to a bloom of sorts, but it is not algae. The cloudiness actually occurs because of a bloom of microscopic life and they can come in the form of bacteria, protozoa, and micrometazoa. To anybody who breeds fish, you may recognize these things as something called infusoria, which is what many fish breeders feed newborn fish fry. While these microscopic blooms may make for great fish food, they make for a really foggy aquarium too.

This bloom is then usually made worse by the fact that we add chlorine removing agents to the water. The chlorine would usually kill those microscopic critters that are fogging up your aquarium, but because you have gotten rid of the chlorine, it gives the microscopic critters a good place to thrive.

Moreover, you then start feeding your fish, fish which produce waste, and also may not eat all of the food you give them. Well, guess what, that waste and extra food is a great source of nourishment for those pesky little critters, thus spurring on their growth and multiplication even further.

How To Fix A Cloudy Fish Tank

Now that we have talked about why your fish tank can become cloudy, especially in the first few days, let’s talk about what you can do to fix the problem.

Something that needs to be said right off the bat is that one of the best things you can do is to wait, be patient, and see if the problem fixes itself, because as is often the case, the microscopic bloom will die down all on its own after a few days. Here are some of the best things you can do to get rid of the cloudiness in your fish tank.

1. Be Patient & Wait It Out

Like everything in life, your fish tank has a natural life cycle, and that goes for all of the critters inside the tank, which of course includes those small critters fogging up your water.

One of the best things you can do is to just wait. The microscopic critters will multiply more and more, but after a while they will reach so called critical mass, where they don’t have enough nutrients and food to support their growth, at which time their population will implode.

Also, sometimes it takes a few days or even weeks for good bacteria to establish themselves in your tank, mainly in the filter, and these are the bacteria that will kill off those microscopic organisms. Therefore, the first thing you want to do is wait, make sure the filter is running properly, make sure to clean fish waste, and don’t overfeed your fish.

In all likelihood this should solve the problem. What you don’t want to do is to start adding chemicals to your tank in the hopes of fixing the problem when you don’t know what the actual cause of the cloudy water is, as this may actually make the problem worse than before.

2. Introduce Good Bacteria

One of the best things that you can do to prevent or get rid of cloudy water is to introduce good bacteria to the water. As we mentioned before, there are some bacteria that need to be in the fish tank because they help to get rid of unwanted organic matter such as microscopic blooms that fog up your water.

Some options to consider include adding packaged bacteria cultures specially designed for aquariums, using gravel that has been covered in bacteria for your substrate, or you can also add some plants.

Plants are great because they are covered in bacteria that will kill the bloom while at the same time also acting as a natural filter too. More on plants here.

If you already have a fish tank and want to set up a new one, you can always try adding a filter sponge from your old tank to the new one because that will already have an established community of beneficial bacteria living on and in it which will reduce the chances of new tank cloudy water.

3. Clean The Filter

Another really important thing that you can do to get rid of that foggy water is to make sure that your filter is clean and in working order, something that is important regardless of whether or not you already have murky water in the tank.

Whatever the case may be, always follow the instructions in terms of maintenance and cleaning for your specific filter. We have covered some of the best aquarium filters here.

The filter is kind of like a life support system that gets rid of any unwanted debris, chemicals and toxins, and organic matter like the microscopic bloom of critters causing the foggy water. Always make sure that all of the filtration components are clean and well maintained.

On a side note, a telltale sign of a filter that is not working right is when the water flow rate starts to slow down. If you notice this happening it is time to maintain and clean your filter. A good working filter should without a doubt be able to remove the organisms causing the cloudy water.

4. Regular Water Changes Are A Must

Another task that many people seem to ignore when it comes to aquariums is a regular water changing schedule.

Think about it, in the wild fish live in open water where new sources of water from upstream and from precipitation are always helping to cycle and change the water in the habitat where the fish live. So, it only makes sense that you need to change the water in the fish tank quite often.

Simply put, one of the easiest ways to prevent or get rid of cloudy water is to get rid of the organisms and their food sources by just changing the water all together. Now, there are extremely dedicated fish owners that will tell you to change at least 75 percent of the water every single day.

While this may be effective at stopping water cloudiness, it is in all reality a bit of overkill. A good rule to follow is to change at least 25 percent of the water on a weekly basis, or even twice per week if you can.

With today’s great tools and technology changing the water in your fish tank really is not that hard. On a side note, make sure that the new water you add is the appropriate temperature for your fish tank.

5. More Is Not Always Better

The final way that you can help to prevent cloudy water from occurring is to make sure that your fish tank is not jam packed full of things. The problem is that fish produce waste, and waste causes these microorganisms to bloom in large numbers.

Therefore, less fish mean less waste, which in turn leads to less organic waste and nutrients that the organisms use as food sources. On that same note, you should also not over feed your fish.

Fish really only need to eat once per day, any more than that is not only a waste of money, but also a sure fire way to feed those pesky fog critters that are sullying the clear waters of your aquarium.

Less can be better, and when it comes to the amount of fish you have in one tank and how much you feed them, more of those things may very well lead to that horribly cloudy water that you are trying to avoid.

You might also want to consider introducing some aquarium shrimp into your tank, they help keep the tank clean.

Commonly Asked Questions

Is Cloudy Water Bad For Fish?

If your cloudy aquarium water is caused by a bacteria bloom, which usually happens 2 to 4 days after adding new fish to the tank, then no, it should not be harmful to fish and will clear up on its own.

However, aquarium water can get cloudy if you have soil or water in the tank that is being stirred up. No, this is not great for fish, as it’s not healthy for any organism to be eating and inhaling sand and soil.

Moreover, decaying fish waste, food, and plant matter may cause cloudy water, and due to the fact that these then release ammonia and nitrates, is also harmful to fish.

Will My Fish Die In Cloudy Water?

If this is caused by a small bacteria bloom, then no, it should not kill your fish.

However, if the water is cloudy due to decaying natural matter, such as plants and food, as well as fish waste, then yes, your fish can eventually die in cloudy water.

All of those things give off ammonia, and if left unchecked can quickly kill your fish in as little as a couple of weeks.

Will A Filter Clear Cloudy Water?

Generally speaking yes, a good filter should help clear up cloudy water. A good aquarium filtration unit will remove decaying fish waste, plant matter, and old food from the tank, therefore removing sources of ammonia.

Moreover, a good filtration unit will also help to add more beneficial bacteria to the water, bacteria which break ammonia down. A good filter should in all reality help to reduce cloudy water, maybe not eliminate it totally, but it’s definitely a great start.

A good way to control cloudy water is to do regular tank cleaning, to reduce the amount of food you give your fish, to perform regular water changes, and to ensure that you have a high quality filter.

Can I Put New Fish In Cloudy Water?

You really shouldn’t do this. If your water is cloudy, more often than not, it is a sign of somewhat poor water conditions, and these can be caused by a variety of factors.

For the most part, you should resolve the issue of cloudy water before you attempt to add any new fish to the mix.


As you can see, preventing or getting rid of cloudy water in your aquarium is not very hard. Just make sure you have a working filter, that there are some good bacteria present, that you change the water often, and that your aquarium is not over stocked. Following the aforementioned tips will in all likelihood prevent cloudiness from ever occurring.

Also remember that the first thing you want to do about cloudy water may go against intuition and common sense, but the first thing you want to do is nothing, at least for a few days, and then if the problem does not go away is when you can start turning to some of the solutions we have talked about.