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Why Is My Oscar Fish Twitching And How To Prevent Them?

Watching your Oscar fish twitching or doing the rapid tail shake may raise many questions in your mind. You must be wondering whether it’s normal behavior or if there is something wrong with your fish that’s causing it to vibrate in a seemingly unusual way.

Well, there are some explanations for it! In this article, we will discuss why Oscar fish keep twitching and how to prevent them.

Why Is Oscar Fish Keeps On Twitching?

why is Oscar fish twitching
Twitching in Oscar fish can be a sign of dominance or aggression. Shaking the tail and/or lower body part also indicate courtship display. Or it could be just that your Oscar is seeing its own reflection or has swallowed something that’s causing a blockage, resulting in twitching.

Should You Worry About It?

It depends on the severity of the twitching.

If your Oscar does it occasionally, you may not need to worry about it. However, if your fish is twitching rigorously, such as shaking out of control, it indicates the onset of a disease that must be treated, or it could be fatal.

Most of the time, it’s a neurological or nerve disorder, which is indeed a concerning situation.

Another factor that determines the seriousness of the matter is a change in your fish’s eating behavior. Have your Oscar been eating as usual? If yes, feel free to rule out the possibility of illness.

Apart from the loss of appetite, other symptoms that help identify a sick fish include lethargic behavior, tucked-in fins, and discoloration, such as pale skin or spots on the body.

Why Is Oscar Fish Turning Gray?

What Causes Shaking and Twitching In Oscar Fish?

When an Oscar fish starts shaking the fin tail rapidly, it can be due to a number of things. To pinpoint a probable cause, one must carefully observe the fish’s behavior.

Below we have shared a detailed overview of some of the most common reasons that trigger the twitching behavior in Oscar fish.

Aggression or Territorial Warning

In Oscars and all Cichlids, twitching is often a sign of aggression and territoriality.

If your fish is violently shaking its tail up and down vertically, it could mean it’s trying to assert dominance or is pissed off by other fish in the tank. Oscars can be seen lip-locking if the other fish decides to hold its ground and take up the fight.

When the action of twitching isn’t directed at the tankmates but aimed at a certain area, it serves as a territorial warning for other fish not to come close.

Oscar fish are dominant in nature, and that’s why they are best kept alone or only with the species they get along with.

Make sure you have compatible tank mates and your tank size is the right fit for the fish in the tank. This is the only way to reduce aggression in your Oscar or any other fish, for that matter.

Mating Behavior

Apart from aggression, Twitching also indicates that there might be love in the air (technically, water), and your Oscar is ready to breed. The vibration of the tail or the back of the body is a part of the courting ritual.

In Oscar fish, the breeding behavior is similar to the signs of territorial fighting. So understandably, it can sometimes be hard to determine what your fish is up to.

Some Oscars get particularly aggressive during mating seasons. It includes lip locking, chasing the mate around the tank, and tail twitching or nipping and biting. During these periods, you may also find Oscar aggressively digging the substrate.

Seeing Reflection on The Tank

This may sound strange to some, but it could very likely be that your Oscar fish sees its reflection and is trying to attack it, thinking of another Oscar.

It usually happens when tank lights are on.

Stressful Environment

When an Oscar fish is stressed, it displays complex behavior. Sometimes it can be twitching as well.

There are multiple stressors, but when we are talking about Oscars, it’s mainly elevated ammonia/nitrite levels, fluctuations in temperature, or an overstocked tank.

Fish Has Swallowed Something

Although it happens rarely, there is a possibility that your Oscar might have eaten something he’s having difficulty passing. This can cause a blockage, distressing the tiny creature to twitch like mad.

If your Oscar fish has been seen digging the gravel lately (which is common during the spawning age), it might have gulped some small rocky bits.

Usually, fish are smart enough to spit out the gravel, but sometimes it passes through the fish’s digestive system and gets excreted.

How to Prevent Oscar Fish From Twitching?

why is Oscar fish twitching
The first thing you need to do is identify why your fish is twitching.

For instance, if it’s out of aggression, as a mating display, or due to the reflection in the glass, you can let your fish twitch all it wants (and maybe enjoy watching it), as it will automatically stop after some time.

However, when unsure of the cause of your Oscar fish vibrating its tail, start with the following methods. And also, ask yourself – does anything out of the normal happened in the tank for the past 24 hours?

Check Water Temperature

Oscars are sensitive to temperature swings. Keep in mind that fluctuations may occur during water changes.

Get yourself an aquarium thermometer if you don’t already have it. For Oscar fish, you must maintain a steady temperature of 74–80°F (23–27°C) at all times.

Measure Water Parameters

If it’s not a temperature issue, it could be poor water quality that’s causing stress to the fish.

Using an aquarium test kit, measure the water parameters, mainly ammonia, nitrate, nitrite, and pH.

Ideally, ammonia and nitrite levels should read zero, nitrates are best kept below 20ppm, and pH should be maintained between 6-8.

Make Water Changes

Perform frequent water changes if your test kit readings show excessive ammonia or nitrite concentration.

Most aquarium water problems can be solved by doing water changes.

Contact a Fish Vet

What to do when the test kit measures nothing unusual, and you can’t seem to figure out the problem behind your Oscar twitching?

In such cases, do not waste time trying to fix the problem yourself. Instead, seek the help of an expert or reach out to a fish veterinarian.

How To Know If Oscar Fish Is Dying?


In Oscars and all Cichlids, twitching is a common behavior often displayed as a sign of aggression, mating, or when dealing with a stressful situation. Besides, twitching can also indicate that your fish sees its reflection in the glass or has swallowed something that’s causing distress.

The only time you need to worry is when your fish is severely twitching or showing signs of sickness, such as loss of appetite, tucked-in fins, change in appearance, lying at the bottom, or hiding. In this case, you must consult a fish vet.