Fish Tank Is Cloudy And Smells Bad? 15 Things To Do

Last Updated on 2023-11-04

If you’re wondering why your fish tank smells bad and is cloudy, then you’ve found the right article! In this article, not only will you find out the common reasons your fish tank appears so murky and stinky, you’ll also learn all the ways to remedy it and stop it from happening again!

So keep reading to find out everything you need to know!

Key Takeaways:

  • Fish tank odor commonly stems from dead fish, overfeeding, decomposing plants, dirty filters, substrate issues, and water conditioner problems.
  • Remedies for a smelly tank involve removing dead fish, regulating feeding to avoid excess food, cleaning or replacing filters, addressing substrate concerns, and accurately measuring water conditioner.
  • Cloudy water reasons include dissolved constituents, bacterial bloom, excessive light, nitrates, phosphates, and substrate disturbance.
  • To clear cloudy water, actions like rinsing gravel, adjusting pH, waiting for bacterial blooms to resolve, maintaining a clean tank, avoiding overstocking, using chemical filters or clarifiers, and adding established biological media can help.
  • Preventative measures involve regular water changes, periodic gravel cleaning, overall tank cleanliness, filter maintenance, controlled feeding, appropriate fish selection, and maintaining proper water parameters.

Why Does My Fish Tank Smell Bad?

No one wants a fish tank that smells bad; it will discourage new fish owners from pursuing the hobby and make old fish owners want to quit. A bad fish tank can make your entire room, or even house, unenjoyable, which defeats the purpose of a fish tank.

The main thing that makes your fish tank smell bad is bacteria, and that bacteria can come from many different sources. These sources include dead fish, excess food, decomposing plants, a dirty filter, your substrate, or your water conditioner.

Reasons for Smelly Fish TankRemedies
Dead fishRemove dead fish promptly.
OverfeedingRegulate feeding to avoid excess food.
Decomposing plantsRegularly remove dead or decaying plants.
Dirty filterClean or replace the filter regularly.
Substrate issuesGently disturb substrate with a gravel vacuum.
Water conditioner problemsAccurately measure and add appropriate conditioner.

Here’s a more in-depth look:

1. Dead Fish

Dead fish are one of the most common cause of fish tank odor. It might take you several days to notice that a fish is dead if it was hidden in an area of the tank you can’t see. The dead fish will be slowly decomposing in the tank which is going to make it stink, as well as being a hazard to other fish..

2. Overfeeding

If you give your fish too much food, the uneaten food will fall to the bottom of the tank and promote bacterial growth. The bacteria will grow exponentially and release gasses that smell bad. 

As well as spiking the ammonia, nitrite and nitrate levels in the tank which can be deadly for your fish.

3. Decomposing Plants

If you have a lot of plants in your aquarium, it may be hard to notice if one has died and is decomposing. However, the plant will be black and slimy and create a terrible decomposing smell. So make sure you’re pruning and caring for your aquarium plants regularly.

4. Dirty Filter

Everything that can create bad smells gets sucked into your filter. In fact, it is common for the filter to be much dirtier than the tank itself; that means it is doing its job. However, if you don’t clean out your filter, your water will smell bad.

5. Your Substrate

If the bad smell from your fish tank smells a lot like rotting eggs, then the culprit is probably your substrate. Sand that has been compacted over time can have areas where no oxygen can reach, and then waste, and bacteria get trapped.

6. Water Conditioner

Sometimes, the water conditioner smells strange. This is because of the chemicals in it. If you put too much into your tank, it may be causing your tank to smell bad.

Many tropical fish swimming in a dirty aquarium with murky water.

How Do I Get Rid of the Smell In My Fish Tank?

Fortunately, just because your fish tank smells, doesn’t mean it has to stay that way. There are plenty of things you can do to remove the smell from your fish tank such as:

1. Removing Dead Fish

The first thing you should do if your tank smells bad is to look for dead fish. Check in all the cracks and crevices of your tank (there may be a lot)! Once you find the fish, carefully remove and dispose of it.

2. Use Less Food

If you see a bunch of food stuck at the bottom of your tank, that is a surefire sign that overfeeding is causing the smell in your tank. First, remove all of the excess food at the bottom of your tank, being careful not to stir it up in the process. Next, be sure to only feed your fish as much food as they can eat in two minutes.

3. Remove Dead Plants

If you can’t find dead fish or any excess food, your next best bet is to look for dead plants. They won’t be hard to miss. They will break apart while you’re removing them, so it is a delicate process.

4. Replace Or Clean Your Filter

Your filter is where all the gunk and goo of your tank ends up. If you don’t clean your filter often enough, all of that goo will start to stink up your tank.

Depending on the kind of filtration system you have, you may have to replace the filter itself, or you may have to rinse it out.

5. Clean Your Substrate

You should never remove the substrate from your fish tank as it harbors a lot of beneficial bacteria which is vital for your tanks ecosystem.

However, if you think the substrate might be causing a stink, then you should gently disturb it with a gravel vacuum, before sucking up any debris.

6. Measure Your Water Conditioner

Have you just been eyeballing your water conditioner? This is not only bad for your fish, but it can also make your tank smell funky. Be sure to properly measure your water conditioner before adding it to the tank.

fish tank,cloudy

Why Is My Fish Tank Cloudy?

As well as a fish tank that smells, your fish tank could also be cloudy. The causes of cloudy water can often go hand in hand with smelly water. With that being said, here are the reasons your tank might be cloudy:

1. Dissolved Constituents

Dissolved constituents are things like heavy metals, silicates, and phosphates. The pH of your water is probably way too high. Dissolved constituents can make even brand-new tanks cloudy.

2. Bacterial Bloom

Bacterial bloom often happens in the first few days or weeks of having a tank. This is because the tank hasn’t had time to develop bacterial colonies that will clear the waste from the water themselves.

And as these colonies start to form they can make the water become incredibly cloudy. Eventually, with time, these colonies will equal out, and the cloudiness will go away.

3. Too Much Light

Too much light will cause algae to grow. You may have the aquarium in direct sunlight, or you could be leaving the lights on for too long. If you notice that the tank is cloudy and green, then this is the most likely culprit.

(Find out how to get rid of algae in your fish tank.)

4. Nitrates

Nitrates will develop over time in the aquarium because of fish waste. High levels of nitrates will feed algae once again causing it to grow out of control and possible making your tank cloudy.

5. Phosphates

Phosphates may be coming from decaying matter like excess fish food or from the water itself. Your tap water may have excess phosphates in it, so you should run a test. Extra phosphates in your water will encourage algae growth, which will turn the tank green.

6. You Disturbed The Substrate

If you recently performed a water change, then you may have stirred up all the silt and dirt in the gravel which has now gone into the tanks water.

Fortunately, if this is the reason your fish tank is so cloudy it should only take a couple of days to settle.

How Do I Get Rid of a Cloudy Aquarium Water?

1. Rinse the Gravel

If your tank gets cloudy right away, it’s probably because the gravel wasn’t washed sufficiently. Drain the tank and transfer the fish into a holding tank. Now wash your gravel until the water is running clear, and set your tank up again.

2. Fix the pH

If your tank is cloudy, it may be because of a high amount of dissolved constituents. This will make the pH of your water high or alkaline. If you think that the water is too alkaline, you should try adding Indian almond leaves or driftwood to it, to increase the acidity.

3.Wait It Out

Bacterial blooms will occur when the nitrogen cycle in your tank is off. During the break-in period of your aquarium is most common, because it will not yet have the bacterial colonies required to self-clean. Soon, there will be good bacteria developed in your tank that will clean the tank for you.

If this is the case, then the best thing you can do is simply wait it out, and wait for the nitrogen cycle to right itself.

4. Keep Your Tank Clean

Remove debris like uneaten food, vacuum the gravel, and perform partial water changes frequently. Only feed your fish as much as they can eat in two minutes to avoid excess food sinking to the bottom of the tank and causing bacteria.

5. Move Your Tank

If your tank is in direct sunlight, that can be encouraging algae growth. So move your tank out of direct sunlight if you notice that your tank is green. In fact, this is the first step you should take if you notice algae in your tank.

6. Make Sure You’re Not Overstocking Your Tank

You should make sure that you’re not overstocking your tank as the bioload from your fish will increase the amount of ammonia in your tank, which could spike a bacteria colony growth phase.

7. Use A Chemical Filter

Using a chemical filter is one of the best ways to keep the water in your tank clean and reduce cloudiness. However, chemical filters are normally the quickest to run out, so you’ll need to change yours every months.

8. Use Clarifier

If you want the cloudiness fixed pronto, then a clarifier can be the best way to do this. Clarifiers cause the particle in your tank that cause cloudiness to clump together, before being sucked into the filter.

If you’re not sure what clarifier to use, I’d highly recommend Seachem Clarity.

9. Seed Your Aquarium

And lastly, you can try adding some biological media from a tank which has already been established to help the beneficial bacteria in your tank grow quicker. While this may not remove the cloudiness right away, it will ensure that the bacteria grows correctly!

How to Prevent a Smelly and Cloudy Fish Tank

Fortunately, you can avoid smelly and cloudy water a lot of time in the first place! To make sure it never happens to your tank again, here are a few things you should try!

1. Change the Water

You should be changing the water in your tank every one or two weeks depending on the size and power of your filter. When you’re changing the water, make sure you’re removing around 10-20% so you don’t end up shocking your fish with different water parameters!

2. Clean the Gravel

You should clean the gravel before you put it into the tank and periodically throughout your tank’s lifetime. The first time you add your gravel to the tank rinse it until the water runs clear.

Then, you can buy a gravel vacuum at a pet store to periodically remove any decaying debris from between the gravel.

3. Keep The Tank Clean

In general, just make sure you’re keeping your tank clean. Remove any uneaten food, dead fish, or decaying plants from the tank. As a rule of thumb you should be cleaning your tank every one to two weeks.

4. Rinse the Filter

Every time you clean your fish tank, make sure you’re cleaning your filter too. Wear a glove, and then take the debris out of the filter’s sponge, as well as this scrub the tubes and casing of the filter in a bucket of the tanks water.

5. Avoid Overfeeding

Fish should only have an eating timeframe of two minutes, so anything they don’t eat during two minutes should be scooped out. Eventually, you will know roughly how much food they will eat. If you let food sink to the bottom of the tank, it will develop bacteria and make your tank foggy and smelly.

6. Get Freshwater Fish In a Big Tank

If you are a beginner, get a big tank and freshwater fish. The bigger tank will stay cleaner because the water won’t be in such a tight space, and the water conditions will stay more stable. Freshwater fish can also handle environmental changes better. 

How Long Does It Take Cloudy Water To Clear?

If the water is cloudy in your tank because of bacterial bloom, then it should clear after a couple of weeks. However, it it’s algae related, then it won’t clear until you fix the issues that caused the algae in the first place.

Does Cloudy Water Mean Ammonia?

If the water in your tank is cloudy because there is a bloom of bacteria, then that means the ammonia, nitrite and nitrate levels in the tank are also too high as well.

Fish Tank Is Cloudy And Smells Bad_ 15 Things To Do


Here are some frequently asked questions people have about why their fish tank smells bad and is cloudy.

Is It Bad if My Fish Tank Is Cloudy?

Bacterial blooms are very common in new tanks, while the beneficial bacteria that eats ammonia is spiking. The water is cloudy because all of the bacteria are free-floating. The cloudiness will settle down in a few days, but if it doesn’t, it’s worth investigating other causes.

How Do I Make My Fish Tank Water Crystal Clear?

However, Healthy plants will naturally filter the water and consume compounds like iron and ammonia, which can cause algal blooms or bacterial blooms.

You can also add clarifiers to your water which are chemicals that quickly fix cloudy water, depending on the cause.

Will Cloudy Water Hurt My Fish?

It really depends on the cause. If it’s because of something decaying in the tank then it could end up being harmful to your fish, however, if it’s algae related, it’s only going to be a nuisance.


There is a lot to learn about keeping fish! If you want to avoid smells and keep your water clear, there are action steps you can take, both to be preventative and to fix an existing problem.

Bad Smells

  • One thing that can make a fish tank smell bad is dead fish. They are the most common cause of odor in fish tanks. Also, overfeeding your fish will cause an excessive amount of food to collect at the bottom of the tank
  • Remove dead fish and only feed your fish as much as they can eat in two minutes.
  • Decomposing plants and a dirty filter will also cause harmful bacteria to grow which will make your fish tank smell bad too. Be sure to get rid of any dead plants and clean out your filter regularly.

Cloudy Tank

  • Bacterial blooms can cause a cloudy tank. Bacterial blooms happen when the tank hasn’t yet developed a healthy bacterial ecosystem. This is something you just have to wait out.
  • Too much light causes algae. Don’t keep your aquarium in direct sunlight. Phosphates and nitrates also cause algae.
  • Rinsing and vacuuming your gravel will help keep your fish tank clean. Make sure you have the right water pH as well.
  • To change the water, remove 25% of the water and replace it with cold, treated water.

If you are just starting off, try freshwater fish in a big tank. Big tanks stay cleaner for longer as they are more stable thanks to the higher volume of water they hold.

Final Thoughts

Now that you know all there is to know about why fish tanks smell bad and get cloudy, you can keep a clean, healthy fish tank that is sure to wow your guests!


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1 thought on “Fish Tank Is Cloudy And Smells Bad? 15 Things To Do”

  1. I am a novice fisherman. I’ve given my fish a lot of food to make sure they don’t starve, but that indirectly causes the smell of my aquarium. The leftovers will rot at the bottom of the aquarium, which will help promote the growth of bacteria, where it can give off a gas that has a terrible odor.

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