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Aquarium filter bacteria – How long can it survive?

aquarium filter bacteria

Aquarium filter bacteria can be a constant worry for us aquarists, we panic if the power goes out and wonder how we will keep our filters ‘alive’.

But is that panic necessary? Here we’re going to take a look at how long our filter bacteria can survive without an ammonia source.

Aquarium filter bacteria

There are lots of theories floating around the internet about filter bacteria.

Not long ago, I saw a post asking how long aquarium filter bacteria can survive without an ammonia source.

This is a great question. There are many occasions where an aquarium might be empty for a while, hospital tanks, quarantine tanks, new setups or if an illness sadly wipes out all of your fish.

Answers to this question varied wildly, with some suggesting that all of the precious ammonia-oxidizing bacteria would be dead within an hour, leaving the filter almost useless and uncycled.

This seems pretty unlikely as that would mean that the average power cut would leave your filter uncycled and your poor fish struggling for life, yet this doesn’t happen.

Is this another topic that has created needless panic within the aquarist community?

So, I thought I would do some research and clear all this up. How long can aquarium filter bacteria last without an ammonia source?


aquarium filter bacteria


Aquarium Filter bacteria

First up, we need to know what bacteria are in our filter. In my ‘Aquarium cycling’ article, I referred to them simply as ‘bacteria 1’ and ‘bacteria 2’, just to keep things easy to follow.

But, these bacteria do have names. If you search the internet you will find them listed under many names and descriptions as there isn’t a mass of information on this topic out there.

According to my research, it is likely that the main bacteria responsible for the breakdown of waste within the freshwater aquarium are ‘Nitrosospira’ (Ammonia) and ‘Nitrospira’ (Nitrite), though much of the research available differs slightly. 


It seems that in many studies, levels of actual bacteria have been found to be fairly low and inconsistent within freshwater aquarium biofilters. 

So what is actually responsible for keeping our aquariums clean?

What is most likely responsible for the majority of your waters filtration of ammonia are microbes known as Archaea. More specifically, Thaumarchaeota. 

These microbes are very similar to bacteria but are classified differently. 


What does aquarium filter bacteria use ammonia for?

Bacteria, and microbes, operate differently to how we do. They do not need energy to move, talk or even think. This means that their fuel requirements are solely for growth and reproduction. 

With that in mind, the amount of energy they consume only relates to how fast they multiply, so a lower availability of ammonia simply means that they multiply at a slower rate. 

Starving these bacteria and microbes of ammonia means that they are unable to multiply, but do they actual starve and die?

From my research, it would seem that no, they don’t. Certainly not as quickly as many aquarists seem to think.


aquarium filter bacteria


How long can filter bacteria survive without ammonia?

I have managed to find a small number of studies on the starvation of nitrifying bacteria and one on ammonia oxidising archaea and the results are fairly surprising – although not too surprising if you consider the above.

It seems that the bacteria and microbes responsible for removing ammonia and nitrite from our aquarium water can survive for quite a while without a food source (ammonia). 

Studies showed that these microscopic populations can survive for at least 10 weeks of starvation, though it is likely that they are capable of surviving for much longer. 

That means that if your power goes out, even for a full 24 hours, there is no need to panic about your filter bacteria. The real concern shouldn’t kick in for at least 10 weeks. 

There is a point to note though, after several weeks of starvation, whilst your bacteria may not be dead…….it may be asleep…..


Sleepy bacteria

After a period of starvation, bacteria can become a little sleepy. It becomes dormant. 

That means that if your aquarium is left for a while without fish in it, your bacteria may survive, but it will need waking up before fish are re-introduced. 

The study I previously mentioned found that after 10 weeks of starvation it took 5 days for the bacteria to ‘wake up’ and begin consuming ammonia again. 

The solution to this is simple, bottled ammonia is widely available and can be added to the aquarium prior to fish being added. An aquarium test kit will be able to tell you when your bacteria is wide awake and doing its job, happily multiplying away. 

You will find both of these in our online shop


Here’s a big ‘sleepy’ yawn from ‘Bain’ the SRM hybrid………

aquarium filter bacteria


What else needs to be considered?

I have scoured the internet but I cannot find much on the survivability of bacteria, or archaea, in anaerobic or anoxic conditions. 

I would expect that the results would be similar to the results during starvation of ammonia as oxygen is a fuel source and not used for ‘breathing’. 

However, as I cannot find any studies on this, I cannot confirm that this is true. 

That means that if you intend to leave your aquarium empty for a while but would like to retain the filter bacteria you have accumulated, you may well need to keep the aquarium running. 


Final thoughts

It seems that there is a lot of unnecessary panic when the power goes out for a few hours, with many aquarists fearing that their aquarium’s filter bacteria is doomed. 

But in reality, it is of little concern. The main concern during an extended power cut or outage would be to keep the water circulating and oxygenated. 

There are many ways to achieve this from a battery-powered air pump to simply stirring up the water every so often. 

The bottom line here is that your filter bacteria and archaea will survive for an extended time period without an ammonia source, but it may need ‘waking up’ if it has been starved for a few weeks. 


If we do have any scientists in the community then please chime in on the comments!!





How long can filter bacteria survive without ammonia?

Aquarium filter bacteria can survive for quite a long time without ammonia. Some studies have shown that it can survive for 10 weeks or more with little detriment to it's numbers.



Nitrospira like Bacteria Associated with Nitrite Oxidation in Freshwater Aquaria

Temporal and Spatial Stability of Ammonia-Oxidizing Archaea and Bacteria in Aquarium Biofilters



Freshwater Ammonia-Oxidizing Archaea Retain amoA mRNA and 16S rRNA during Ammonia Starvation

Growth at Low Ammonium Concentrations and Starvation Response as Potential Factors Involved in Niche Differentiation among Ammonia-Oxidizing Bacteria

About the author

James @Seriously Fishy

I am a fish keeping enthusiast with over 20 years experience. I currently keep American Cichlids (CA) which are my favourite fish to keep so far. I started Seriously Fishy as I noticed a large volume of people on various web pages looking for help with Aquarium basics. I created the first Seriously Fishy book to solve the issue in 28 pages, that led to the Seriously Fishy UK fish forum and blog.

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