How to Get Rid of Bacterial Bloom in a Saltwater Aquarium?

How to Get Rid of Bacterial Bloom in a Saltwater Aquarium?

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Many issues can adversely affect a saltwater aquarium. Since they’re delicate ecosystems, it’s essential that everything remains in perfect balance. This means it takes dedication and effort on the part of the caretaker to stay on top of anything goes awry. Bacterial Bloom is one of these types of problems. Often a predicament for newer saltwater tanks, Bacterial Bloom can also occur in established tanks.

So, how do you get rid of a bacterial bloom in a saltwater aquarium? You will have to clean your filter, do a 25-30% water change and clean the gravel as soon as possible.

How to Get Rid of Bacterial Bloom in a Saltwater Aquarium

If you’re trying to establish a new tank, allow the cloudiness to occur. Don’t touch or change anything because it’s a necessary process in building a healthy Nitrogen Cycle. Also named New Tank Syndrome, this is something an aquarium must experience in order to be appropriate for fish and plants.

If you notice a second Bacterial Bloom after adding fish, understand it’s happening because more organic matter is present. This is another reason why only a few fish should become part of the tank at a time. It will allow the ecosystem to balance itself out without causing stress to the fish.

Established Tanks

However, Bacterial Bloom in established tanks means this can be a problem that can grow exponentially if left unchecked. More than likely, it will disappear without intervention. Do the steps below if the milky muck doesn’t dissipate on its own:

  1. Check ; Clean the Filter:  Rinse the filter off with cold water to remove clogging, blocking or anything else forcing it to malfunction. Check that it’s powerful enough for your tank size along with the number of fish you have. Check with your aquarium store if you aren’t sure.
  2. Perform a Water Change:  Do a 25% to 30% replacement with prepared water. Ensure you add conditioner and salt appropriate for the amount you remove in relationship to the tank’s size. Do this for two to three days until the Bacterial Bloom is no longer an issue.
  3. Clean the Substrate:  With a gravel vacuum, clean the substrate while ensuring you siphon out all feces and uneaten food. Being a little meticulous with this will greatly prevent Bacterial Bloom. If you notice excessive waste, your fish eats too much.

Quick Methods with Commercial Products

For a quicker method, use an enzyme or introduce beneficial bacteria. Both of these will help to clear up Bacterial Bloom within a matter of days. Always ask your local aquarium store clerks with any of your questions and read the package directions well.

What is Bacterial Bloom?

Bacterial Bloom is when the bacterium in your tank grows exponentially due to too much organic waste and debris. It reproduces rapidly and you have to remove the bacteria as soon as possible because it can rob the tank of its oxygen.

Even though this happens more in newer tanks, it can happen in established ones too if the organic debris gets out of control. But, it seems that Bacterial Blooms are more apparent to tanks without any organics present, such as is the case with newer ones. The water’s chlorination declines which enables and supports colonies of bacteria.

The Presence of Two Bacterium 

In a normal tank with a healthy Nitrogen Cycle, there are two types of bacterium. The first is Autotrophic Bacteria and it uses light and chemicals to synthesize its own food. Autotrophs are good because they provide assistance with water filtration. In fact, Bacterial Bloom is not the result of excessive Autotrophs.

The other type is Heterotrophic Bacteria. This kind feeds on things like decaying algae, dead fish, dead bacteria and fecal remains. These mineralize, or breakdown, matter to regulate the tank’s sensitive balance.

But, Heterotrophic Bacterium is the culprit for Bacterial Bloom. It means nutrients such as nitrates, phosphates and ammonia are exorbitant from all the available organic debris. This can be dangerous to aquatic and plant life in the tank.

How Do You Know Bacterial Bloom Is in the Tank?

Bacteria is a requirement for a healthy Nitrogen Cycle, indicated by a slimy residue called “bio film.” But, too much will cause a sudden uptick in the amount of bacterial colonies. These are specifically ones which suspend in the water column.

They get so out of control they can cause the aquarium to become opaque. In some cases, it can even be difficult to see the fish because of how Bacterial Bloom reduces visibility. This will look white, cloudy, light brown or milky in the water.

Why Do Bacterial Blooms Appear?

Any spike in the tank’s available nutrients will immediately set the stage for Bacterial Blooms. For new tanks, this is normal and shouldn’t be any cause for alarm. This should dissipate after a few days. It’s happening because of fluctuations in chlorine levels, which allow bacteria to flourish and begin consuming any available organic matter.


But, there could be a myriad of other possibilities as to why Bacterial Blooms are appearing in an established tank. Overfeeding is most often the reason. So, only give enough flakes that fish can eat in a matter of minutes. Tinier meals throughout the day is optimal. If that’s not possible, then twice per day will suffice.

Dead Fish or Plant Matter

What also causes Bacterial Bloom is not removing dead fish or dead plant matter in enough time. What’s more, if you add too many fish at once, it can tax the ecosystem of the tank and cause Bacterial Bloom. So, only add a few new fish in sparse intervals.

Substrate Disturbances

Another important but little known cause of Bacterial Bloom can happen because of a severe disturbance or shift to the substrate. Things like a hard bump or violent shift can release food and bacteria trapped underneath the tank’s gravel. This can and will rapidly replicate into a full Bacterial Bloom problem.

Equipment Breakdowns

In the event the filter or pumps stop working, it can create a breeding ground for bacterial reproduction. Always check on the working condition of your equipment. Keeping to a schedule of cleaning and maintenance of these things will deter clogging.

What Happens When Bacterial Blooms Appear?

Because bacteria rely on oxygen, it will absorb more and more as it grows and reproduces. This can lower the oxygen quality for your fish. Although this is only risk to your fish when Bacterial Blooms occur, it can be stressful.

If it’s bad and thick enough, your fish won’t be visible. In other cases the fish won’t be able to breathe and will try to gasp for air or jump out from the tank. This means you should agitate the water to get more oxygen into it. You can either angle the nozzle at the surface or include an air stone.


Bacterial Bloom shouldn’t often be a problem. But, when it does happen, you have to prevent matters from getting worse. The best way is by performing regular partial water changes. Also, adopt good maintenance habits like not overfeeding and monitoring the equipment.

See Also:
Can Fish Die from Overfeeding
How to Treat Ich in a Reef Tank with Garlic
How to Clean Fish Tank Gravel Without a Vacuum
How Fast Do Cory Catfish Grow?