Why Is My Betta Fish Inactive & Lethargic?

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Every Betta fish owner knows how active these colorful fish can be while swimming around their tanks and exploring all corners of their tank and it is pure fun to observe them.

But when a Betta becomes slightly lethargic, this can often bring many worries. And certainly, the main question owners ask themselves is why is my Betta fish not active?

It can be quite frustrating not knowing what brings such odd behavior and whether there is anything that needs to be done. That is why we are sharing an ultimate guide of the various reasons which can bring a decreased activity in Bettas and how to distinguish them.

Poor Water Quality

Sadly, poor water quality is one of the most common reasons for a Betta becoming lethargic. Tanks that do not feature a proper filtration system and tanks where water has not been changed for a while will often measure abnormal parameters.

This can also happen frequently when owners tend to overfeed their Bettas, as food leftovers and increased fish waste sink to the bottom and bring to spikes in ammonia.

A Betta which is faced with abnormal conditions will first gasp for air, but will later quickly lose its normal body functions. It will stick to the bottom of the tank, being extremely lethargic. Sometimes there can be visible signs as red or burnt skin, too.

If you suspect on poor water quality, the simplest yet most effective to verify that is by using a freshwater testing kit. This will show ammonia, nitrate, nitrite and pH levels. If these show any oscillations, please perform a partial water change at soon as possible.

Low Water Temperature

Betta fish are tropical fish that require tropical temperatures. If water is outside the range of 74- to 80-degrees Fahrenheit, they will not be able of absorbing warmth from it anymore and their immune systems will therefore become slow and compromised.

Remarkably similar to poor water quality symptoms, Bettas that are suffering from cold will also stick to the bottom of the tank, unable to move. Their tiny hearts will slow down by much and they may even fall into a coma.

If you notice your thermometer showing decreased levels, it is necessary to warm up the water as soon as possible. However, try performing that gradually, to avoid any further temperature shock.


Finally, a perfectly safe reason for a Betta not being active! If your fish is not showing any signs of distress and the water parameters are regular, it may be sleeping. Do not worry about it having open eyes, as Betta fish do not have eyelids.

Just as people, these amazing pets mostly sleep during nighttime. However, they also love to take occasional naps during the day, too. So, if you see your Betta resting but still slightly moving its mouth and gills, this probably means that it is having a nice nap.

Bettas can actually sleep in various positions and even on various surfaces, although most of them seem to enjoy plant leaves as comfy beds.

If you are still worried and would like to make sure that your Betta is simply resting, try approaching the tank or turning an additional light on. This should wake it up and it should resume swimming normally.

Swim Bladder Disorder

If your Betta has been eating too much or having trouble with infections or even spending some time in unsuitable water conditions, this can bring to the disorder of its tiny swim bladder.

Bettas which suffer from such disorder are quite easy to spot, as they have literally no ability to swim normally. They can either keep sinking to the bottom of the tank or floating back up without the possibility of controlling their moves. They can also swim on just one side or become extremely lethargic.

If you suspect your aquatic pet suffering from such a disorder, it is first necessary to understand the reasons behind that being able to cure it. For instance, constipated fish will show a clearly bloated belly and will refuse to eat.

This disease can be treated by fasting your fish for 2 or 3 days or even by offering it some fibers. A quarter of a previously cooked and peeled pea can do miracles.

Furthermore, Bettas that suffer from any kind of infection will often shake or have clamped fins. In such cases, it is necessary to quarantine the affected fish and treat it with medication.


There are many different either internal or external parasites that can cause a Betta to act lethargic.

If you notice any discoloration or any new visible spots or marks across their bodies, these may be external parasites and your fish will often try rubbing them off against plants or tank decorations.

On the other side, internal parasites are more difficult to notice (other than white stringy poop) but they will surely showcase some behavioral changes in the fish.

If you suspect parasites attacking your Betta, please consult your vet. He or she will help you detect which one is it and will consequentially suggest the best treatment. Either way, you will probably need a spare quarantine tank.

Old Age

Just as old people have trouble running as they used to when they were younger, the same happens with Bettas. Once they reach old age, they will have more trouble moving as they used to and they will start spending more and more time resting. Their metabolic system will slow down and poop less.

If you are a proud Betta owner for a while now, and your fish starts becoming less active but it still accepts food and there are no visible signs of illness, it may be a good indication that your Betta is now old.

Wrapping Up

If you notice a change in your Betta’s behavior, it can be worrying. However, some changes are normal, while others can be stopped if spotted early.

But remember, the easiest way to avoid unwanted situations is by offering your Betta a clean environment, a healthy diet, and constant monitoring.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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