Shrimp Behavior: Why Do They Keep Swimming Around?

Shrimp Behavior: Why Do They Keep Swimming Around? Reasons and explanations

If we want to keep our shrimp healthy and happy, we need to understand what they are saying with their behavior. For example, what does it mean, when they start swimming around frantically in the tank?

Actually, it is not uncommon for shrimp to swim erratically. They do that all the time during mating. At the same time, jerky and darting motions can be the sign of stress that can include problems with water quality, predators, diseases, acclimation, etc.

Without further ado, let’s take a closer look at the main reasons why shrimp keep swimming around and what you need to do in case of an emergency.

1. Shrimp’s Mating Ritual – Craze Dances

In shrimp, the mating and breeding processes are closely connected to molting cycle.

In short, mature females have eggs in the ovary, which is located at the junction of the cephalothorax (carapace) and with the tail (abdomen). So, when they are released eggs from the ovary, they travel to the uterine tubes for fertilization.

However, in order to transfer the eggs from the ovary, shrimp have to molt (shed their exoskeleton). It makes the newly molted female cuticles soft and flexible, which makes fertilization possible.

At the same time, the newly molted female starts releasing certain pheromones into the water. It is the signal for the males that she is ready to mate.

These signal-carrying chemicals have an overwhelming effect on males. They cannot resist it and, as a result, male shrimp start swimming around the tank like crazy. They want to find that female and mate with her.

The mating process lasts only several seconds, but pheromones stay in the water column for an hour or even longer. Once, pheromones lose their potency, the restless behavior and crazy dances stop immediately.

Related articles:


Dwarf shrimp need hiding places to be happy. A LOT!  Seriously, it is absolutely crucial to minimize stress to your shrimp by giving them a lot of places to hide.

Now, what does it have to do with the topic of this article?

The point is that for females molting (mating) can become really dangerous if they are exposed and chased by multiple males.

Keep in mind that after molting, they are soft and weak. So, males can easily stress or even harm them in this frenzy state.

2. Stress Behavior

Now, let’s talk about the negative side of swimming around the behavior in shrimp tanks.

In spite of their small size and rather simple nervous system, dwarf shrimp can become stressed just like all other animals.

Shrimp often become stressed in response to:

  • inappropriate quality of their environment, (bad water parameters),
  • incorrect acclimation,
  • large water changes,
  • toxins,
  • parasites and/or diseases,
  • incompatible tank mates.

Is swimming around behavior the only sign of stressed shrimp?

No, it is not. There are several signs of a stressed shrimp. It can be:

  • lethargy,
  • lack of appetite,
  • loss of color,
  • molting problems,
  • decreased growth,
  • reduces fertilization success,
  • loss of the eggs,
  • decreases fecundity,
  • erratic swimming (yes, it is only one of the signs).

2.1. Inappropriate Quality of Water

Bad water quality is probably the main reason why shrimp can swim like crazy in the tank. Inappropriate water parameters can cause lots of stress to the shrimp if they are poorly maintained. Personally, I would definitely start with this one if you noticed this type of behavior.

In shrimp keeping, the most important thing is the consistency of water parameters. Dwarf shrimp do not like changes. Actually, this rule should be written in stone!

All these water parameters can cause stress to the shrimp if they are not in the optimal range. Thus, any changes in shrimp behavior should be attended immediately.

Important: NEVER put dwarf shrimp in an uncycled tank. It is a horrible idea! Your tank must be fully cycled. Dwarf shrimp cannot survive in the uncycled tank or during the cycling period.


  • I highly recommend reading my articles about all these water parameters. They are all shrimp-focused and have lots of useful information.
  • Test your water.

Without testing your water parameters you will not even know what could go wrong. In other words, you are pretty much flying blind and hoping for the best.

Therefore, you need to have a master test kit that can estimate the real condition of the water parameters in the tank.

I know that some people prefer to save a few bucks, and test their water in local fish stores. OK, but what can they do in case of an emergency? Let’s say if something goes wrong at 4:00 a.m. on Sunday?

Therefore, I strongly believe that everybody should have a test kit. It should be one of the first things you buy. It is a must-have tool to know what is going on in your shrimp tank.

API Master Test Kit (check the price on Amazon).

2.2 Incorrect Acclimation

So you just bought a whole bunch of new shrimp and dumped them in your tank, only to find out that they start frantically swimming around round the tank, looking like they want to get out.

Unfortunately, incorrect acclimation is one of the leading causes of death for newly acquired shrimp.

Unlike fishkeeping, where the drop and flop acclimation method is pretty popular, we absolutely cannot do that with the shrimp.

This can be especially important for beginners who do not understand the importance of this procedure.

Do you remember me saying that dwarf shrimp do not like changes?

Well, basically, it is the same problem but from another angle. Shrimp are quite sensitive animals. Abrupt changes in water chemistry and temperature are very dangerous.


We need to acclimate them properly before adding them to the aquarium.  

The idea is to slowly introduce your new shrimp with water from the tank until they are fully adjusted and can live well in it again.

Check out my article “How I Drip Acclimate Shrimp and Why”, you will find:

  • step-by-step description,
  • explanation of every step and why I do things the way I do.

2.3 Large Water Changes

Large water changes (more than 20%) usually make shrimp swimming all over the aquarium. It is a fact but why?

Assuming that new water does not contain any harmful chemicals, there is only one reason for that – large water changes affect water parameters in the tank.

And what is worse, it happens very suddenly for the shrimp. The downsides are pretty significant, large water changes will likely:

  • stress the shrimp out,
  • prevents them from molting (“White Ring of Death),
  • cause them to prematurely molt which can lead to death in extreme cases.

Note: Some aquarists may say that they have been doing 25 and even 50% water changes and it was OK. It can be true, for example, Cherry shrimp are considered to be one of the hardiest shrimp in the hobby.

However, being fine and thrive are completely different thing. There is no need to test their limits.


I have to repeat it once again.

Shrimp require a stable environment to thrive. Going along with this theme, try not to do sudden large water changes.

But, what can we do if we have to do large water changes because of … any other reasons?

In this cases, instead of doing one big change slowly drip new water into tank so that they have time adjust before more substantial change is made.

You can also read “How to Do and How Often to Do Water Change in Shrimp Aquarium”.

2.4 Copper, Hydrogen Sulfide, and Other Toxins

Toxic substances come in contact with the shrimp through its gills rather than skin (hard shell), which is a far more direct and dangerous way of intake.

The toxins go straight into their bloodstreams without being filtered by other parts of the body that might serve as protection from them.

This means toxic levels can quickly weaken shrimp to make it susceptible to disease and other pathogens if not treated appropriately immediately.

In many cases, the accumulation effects of the toxins can be revealed by behavioral change – shrimp quickly respond in the form of increased movement.

The list of toxins, any shrimp keeper should be aware of, include:

  • Copper contamination (Cu, even in small numbers can be lethal).
  • Hydrogen sulfide (H2S, it smells like rotten eggs).
  • CO2 poisoning (CO2 levels in excess of 25-30 ppm are dangerous for shrimp).
  • Chlorine, chloramine, heavy metals (These chemicals irritate the gills and block the oxygen-carrying cells, leading to suffocation in shrimp).
  • Pesticides.
  • Medications and fertilizers (Some aquarium additives may contain copper, or other toxic elements. Thus, they have to be used with caution).


  1. Read product description. A lot of manufacturers will term their products will tag their products as ‘shrimp safe’ but you must study the composition of these products and pick out the most suitable one for your aquarium.
  2. Quarantine everything. The only way to prevent pesticides is to quarantine everything and especially plants before putting them in shrimp tanks.
  3. Provide enough oxygen. The hydrogen sulfide can be effectively neutralized in the tanks with oxygen. Once hydrogen sulfide gas connects with oxygen it will return to sulfate form, which is not toxic.
  4. Pollutant binders. Age and treat your water with a water conditioner prior to use. By doing so you will eliminate this problem right from the start.

For more information, read my articles:

2.5. Parasites and/or diseases

In some cases, shrimp that are sick or heavily parasitized may start zooming around.

Is it a common response? No, it is not. However, I have to include this as a potential reason anyway.


Unfortunately, there are not many diseases and parasites that we can treat successfully in shrimp tanks.

Some methods are very risky and do not guaranty any results.

I have done extensive research on this topic. On my blog, you can find articles based on personal experience, the experience of one of the best shrimp and fish keepers, and especially published studies.

However, to get a general idea, I’d recommend starting by reading “Understanding Dwarf Shrimp Diseases and Parasites”.

2.6 Incompatible tank mates  

In my experience, one of my tanks was invaded by a dragonfly nymph. I could not understand why my shrimp did not want to breed. In addition, their behavior was a little bit strange.

Although they did not dart from one side of the tank to the other, they reacted very fast and jumped at any move.

It took me several weeks to find out the culprit! After that their behavior became normal.

I believe that shrimp can feel the predators even when they do not see them and it can also affect their behavior.


Be very careful with shrimp’s tank mates. Avoid or do not keep shrimp with:

  • Larger or aggressive fish (shrimp will start hiding).
  • Any Crayfish species (be ready to lose some shrimp from time to time).
  • Most freshwater crab species (be ready to lose some shrimp from time to time).
  • Dwarf frogs (be ready to lose shrimp).

For more information, you can also read:

Can Erratic Swimming be a Simple Characteristic of Your Shrimp?

No, it can’t. It is true that dwarf shrimp are pretty active animals and always move around the tank in search of food. However, unlike fish, crayfish, and crabs they do not have personalities in the absolute majority of cases. Shrimp’s behavior is pretty standard.

How to tell apart shrimp’s mating ritual from stress signs? 

You need to observe other shrimp. Other large females or juveniles do not participate in this crazy dance. They will keep doing what they usually do – eating.

However, if you have any doubts, if shrimp started swimming around the tank right after you changed something (feeding them, dozing plant fertilizers, doing water changes, planting plants, introducing new livestock, etc.) – it might be a very bad sign.

In Conclusion

Dwarf shrimp can zoom around the tank for two main reasons, it can be:

  • Some form of the mating ritual or
  • Reaction to the stress.

You need to understand their requirements and know when shrimp are happy. It will allow you to notice any erratic behavior before it too late.

So, if you see your shrimp swimming frantically out of blue, it can be a sign that something in the water is bad for shrimps, that is why they will rush about the tank looking for an escape.

You have to address it immediately!

  • First thing first – remember what was the last thing you did and change/remove it if possible.
  • Test your water parameters for ammonia, nitrites, and nitrates.
  • If you have ammonia, nitrites, nitrates, or copper intoxication – do water changes first.
  • Make sure that pH, GH, KH, and temperature do not fluctuate.
  • Ideally, you need to have a quarantine tank always ready.

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