Why Are Your Tropical Fish Twitching? 3 Reasons 

With their vibrant colors, tropical fish can be relaxing to watch as they swim about their day. But once in a while, your fish may act strange. For example, why would a tropical fish twitch? 

Your tropical fish may be twitching due to extreme stress. Something may be wrong in the fish’s tank, the fish may be bullied by a tank mate, or the fish may be ill. On occasion, the fish may just be itchy.

This article will cover why tropical fish twitch and how to solve the issues to return your fish to their healthy selves.

Reasons Your Tropical Fish Is Twitching

Your Fish Feels Itchy

Just like with people, a fish’s occasional twitch probably isn’t anything to worry about. A seemingly random twitch or rubbing against something in the tank may be your fish’s version of a good scratch. For more info, including how to tell if a fish is simply itchy or if it’s something to be worried about, read this article

However, if the twitching is constant or severe, you may need to look at other factors.

Something in the Water Is Wrong or Out of Balance

Stress is the main reason for a fish to be constantly twitching. This involuntary behavior can manifest in just one part (e.g., the fins) or the entire body. If your fish is rocking back and forth, that’s a type of twitch known as ‘shimmying.’ 

One reason your fish may feel stressed is due to environmental factors, such as: 

  • Poor water quality
  • Uncomfortable temperatures 
  • Hunger
  • Boredom 
  • Poor water circulation 

The Fish May Not Be Getting Along With the Others

It’s possible that one or more of your fish are getting bullied by their tank mates. Just like people, bullied fish become stressed, which can manifest as twitching. It’s possible you may have inadvertently mixed two different species (or two different personalities) that just clash with each other. 

If your fish are the freshwater variety, here’s an article on freshwater fish that can live together.

The Fish Is Sick

Finally, a tropical fish may twitch because of illness. Signs of a sick fish include:

  • Irritated/swollen gills or eyes
  • Missing scales
  • Damaged-looking fins 
  • Dull color
  • Not eating
  • Lethargic behavior

How To Keep Your Tropical Fish From Twitching

Keep the Water Temperature and Chemistry at Optimal Levels

When your fish seems stressed, the first thing you should do is check its tank and ensure that the environment is suitable for your pet. 

For tropical fish, the water should be between 76-80°F (24.5-26.7°C). You can install a heater for your tank, such as this Orlushy Submersible Aquarium Heater (available on Amazon.com). The heater is available in multiple power levels for different tank sizes and has a thermometer to help you gauge the water’s temperature. 

Likewise, pH levels and the overall water chemistry (nitrate, oxygen, and ammonia levels) must be checked regularly. There are multiple test kits you can use to check for pH, water softness, and other vital statistics. One option on Amazon is these PULACO Aquarium Fish Tank Test Strips (available on Amazon.com). Each strip tests the levels of pH, nitrate, nitrite, chlorine, carbonate, and water hardness. 

This YouTube video covers the basics of pH, GH, and KH levels in an easy-to-understand format:

Clean the Tank Once in a While

If you can barely see anything in the tank due to all the algae, it’s probably time to clean it up. You can also install something like the Aqueon Aquarium Algae Cleaning Magnets (available on Amazon.com). It allows you to clean the tank from the outside, and it comes with a 90-day warranty.

In case you want to know how much water you need to change, I’ll point you to this other article.

Nip the Bullying in the Bud

Watch how your fish behave towards each other, especially at feeding time. If a fish is frequently nipped at or chased, that can lead to high-stress levels and twitching. Check out this article on WebMD for more information on fish aggression and how to reduce it.

Get Help From a Veterinarian

If there’s a veterinarian in your area, it may be a good idea to give them a call ASAP. Ideally, your vet should be experienced in treating tropical fish. If you have a betta fish and you notice them swimming sideways, here’s a vet’s take on the matter. 

Final Thoughts

As soon as you see one of your tropical fish constantly twitching its body, you should examine the tank for any sources of stress — such as water temperature, pH, bullying from tank mates, and illness — and address them as soon as you can.


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