Why Is My Aquarium Cloudy?

Like algae bloom, aquarium water can also get cloudy and look milky.
This is called bacterial bloom, and it isn’t always an emergency.
In fact, it is very normal for your aquarium to experience this if it is new.
There are, however, other reasons that could be causing the bacterial bloom.
Those reasons can be a lot more serious and will require intervention.
If you want to learn all about what cloudy aquarium water is, what causes it and how to get rid of it, keep reading.
What Makes Aquarium Water Turn Cloudy?
Aquarium water often becomes cloudy when you have set up a new tank.
The water will turn cloudy when microscopic organisms start to try to establish themselves in the tank, which basically had no life in it before.
The water will typically be clear for the first few days after setting up the aquarium, then it will begin to get cloudy as the organisms do their work.
Because the beneficial nitrifying bacteria that will filer the tank’s water has not yet had the chance to colonize the tank, all organisms are in a free-for-all.
This tends to last for around a week, and after that the water will return to normal.
The cloudiness itself comes from the bacteria and microbes taking advantage of the nutrients and minerals in the water.
This enables them to multiply at a rapid page, making the water appear cloudy or milky.
Often this situation can also be related to there being too many fish in the tank or when people give their fish too much food.
When this happens, the microbes and organisms in the tank have even more food and will thrive.
Natural Reaction As The Tank Finds Its Balance
As we mentioned before, this bacterial bloom, or cloudy water, often happens with new aquariums.
When this is the case, there really is nothing to be worried about.
Decaying Plats, Fish, Or Excess Food
The second reason your aquarium water could be turning cloudy is because of all the dead organic matter in the tank.
Whether this is from overfeeding, dead plants or fish, it will cause reproduction of heterotrophs to speed up so that the organic matter is broken down.
Because they reproduce too quickly, they cannot attach to the surface, causing the bacterial bloom.
Are There Any Dangers to Cloudy Water in Your Aquarium?
Bacterial bloom is not a dangerous phenomenon.
The only possible risk of it is oxygen deprivation.
The bacteria need a lot of oxygen to survive in the environment, so the oxygen content of the water will drop significantly.
To combat this issue, increase the aeration in your tank.
You will know that your fish are struggling to get enough oxygen if you see them gasping for air on the water’s surface.
Preventing The Water In Your Aquarium From Turning Cloudy
There is not always a lot you can do to prevent bacterial bloom from happening in new fish tanks or aquariums.
However, there are ways to prevent it from happening while the tank is in use.
Do Not Overfill Your Tank With Fish
Like algae bloom, bacterial bloom can also be brought on by having too many fish in your aquarium.
Having too many fish for the size of your tank will result in there being too much waste and microbes in the water.
Not only that, but having too many fish in one tank can be harmful, as ammonia and nitrite levels will rise.
In the Filter, Add Activated Carbon Media (Carbon Pads or Loose)
By using either carbon pads or carbon media, the water will be filtered and stay clear.
Using these carbon medias will also absorb the nutrients that the bacteria and microbes feed on in order to bloom.
Do Not Feed Your Fish Too Much
Overfeeding the fish will also contribute to bacterial bloom.
As there are no nitrifying bacteria in the tank to break down the food waste, the bacteria that cause the cloudy appearance will use it.
This enables them to keep multiplying.
It is important to note that even though it may sound bad, you do not need to feed your fish every day.
Fish are able to live happily, feeding only a few times a week.
So even if you do not feed your fish for three days, or reduce the amount of food to combat the bacterial bloom, they will be just fine.

Feeding your fish too much will do more harm than good, as it will allow bacteria in the tank to take advantage of all the food that is not eaten.
You should only feed your fish as much as they can eat in two minutes or less.
More than this will cause problems in the future for both you and the fish.
Test Your Aquarium Water Frequently
As soon as the water in your aquarium starts to look cloudy, you should always get the water tested for ammonia and nitrites.
If the results come back as zero, there is no cause to be concerned, and you should just wait it out.
If, however, you have tested your water and there is ammonia and nitrites in the water, you can do a 25% water change to reduce the levels.
Seed Your Aquarium
You can seed your aquarium if you have a well-established tank that is healthy.
To seed your tank with bacterial bloom, get a handful or two of gravel from the healthy aquarium.
Doing this will get some beneficial bacteria from the healthy aquarium to the one with cloudy water, which will speed up the water clearing.
When you buy a tank in a store, many of them come with bio-sponges and wheels or filter cartridges.
These devices are stocked with bacteria and are another way of seeding your aquarium.
These small devices help the new tank get its biological and bacterial balance going.
Curing Your Outbreaks Of Cloudy Water
There is no need to worry when cloudy water makes an appearance.
The best thing you can do it wait it out.
While this might not be pleasant, it is the easiest and best way to move forward.
There are a few minor things you can do to prevent bacterial bloom from occurring (mentioned above) but in general this phenomenon is nothing to worry about.
Frequently Asked Questions About Cloud Aquarium Water And What To Do About It
There are probably a lot of questions you have regarding bacterial bloom.
Are there any measures you can do to help, or anything you must not do?
Below are a few common questions that people have when it comes to cloudy water in their aquariums.
I hope this answers any questions you might have or be worried about.
What Should I Do About The Cloudy Water In My Aquarium / Tank?
As mentioned before, you do not have to do anything when your aquarium water becomes cloudy.
You can make sure that the water is properly aerated so that your fish have an earlier time, but other than that all you need to do is have some patience and wait it out.
Do I Need To Change The Media Filter Or Get A New One When The Water Goes Cloudy?
Definitely not.
The last thing you should do is mess with the filter if your aquarium’s water is cloudy because it is a new tank.
Doing this will actually cause more harm than good.
There is the risk of getting rid of the good bacteria that are trying to establish in the tank if you clean or remove the filter.
In general, if your filter looks like it needs to be cleaned within the first 30 days of getting your tank started up, you are probably over feeding or overstocking your tank – or both.
Should Live Plants Be Added To The Tank?
Adding live plants to your tank is almost always a good idea.
Live plants have good microbes and bacteria on them.
This good bacteria can help the tank establish a balance.
Additionally, adding live plants means that the microbes that cause the cloudy water are unlikely to get the nutrients they need, because the plants will take them all.

Plants will also consume the ammonia that is generated by the fish in the tank, as well as the uneaten food.
Lastly, the attrition of live plants mean that oxygen will be produced during the day.
This will help the fish waste, dying bacteria and uneaten good get broken down, clearing the water.
Do I Need To Add Beneficial Bacteria To The Aquarium When The Water Goes Cloudy?
New bacteria should be added to your aquarium every time new fish get put in or when the water is changed.
So, yes, you should definitely add bacteria to your tank.
You can do this by seeding your aquarium.
Do I Need To Change The Water More Often When It Goes Cloudy?
Changing the water in your aquarium while it is cloudy will result in clear water for a brief time (around 24 hours), but could worsen the cloudiness cause of the added nutrients in the fresh water.
You should not have to change the water in your tank while the water is cloudy, but you need to make sure that you carry out proper tank maintenance at all times.
How Long Does a Bacterial Bloom / Cloudy Water Last?
In most cases, the bacterial bloom, or cloudy water, will only last one or two days.
After two days, everything should either start to stabilize or already be stabilized.
If the cloudy water lasts longer than two days, check to make sure that there are not any minerals leaching from the tank decor.
Additionally, check to see if there is any microscopic debris in the water.
This debris could be making the water cloudy.
If this is the case, check your filters to make sure that they are working properly.
Can Cloudy Water Harm Or Kill My Fish?
In most cases, no, bacterial bloom is not harmful to your wish.
However, in severe cases, the cloudy water can be harmful to your fish.
This is because the bacteria use a lot of oxygen and will reduce the oxygen levels in the tank a lot.
If you want to combat this, make sure that you aerate your tank so that your fish can breathe.
Final Thoughts
Cloudy water in your aquarium can be a confusing and concerning sight, but it is nothing to be concerned about.
As long as you follow the above steps and take proper care of your tank from the start, the cloudy water you experience will resolve on its own.
Bacterial bloom is not a serious problem, but it is also very preventable if you follow the proper measures.
When you buy a new tank and are new to the world of aquariums, do not be alarmed if you wake up one day, and it looks like someone has poured a carton of milk into it, it is a natural process.