Caring for your fish tank isn’t as easy as it sounds. Hundreds of issues can affect your fish’s life if you don’t give them enough attention, one of which is shimmying, meaning that your fish is shaking from side to side continuously. At first glance, it can be extremely concerning.

Why is my fish shaking? You must be wondering. There are many reasons for this problem, and you should be careful while analyzing your fish’s symptoms. Depending on your fish’s type, you can apply different strategies to help your little mollies.

Scroll down and learn more about this case!

yellow fish

Symptoms Of Fish Shaking

The situation when your fish tremble uncontrollably is usually called shimmying. It is related to uncommon behavioral or postural gestures that indicate your fish’s unhealthy status. Some of the most significant traits are head shaking, heavy breathing, yawning, or clamped fins.

If the said traits happen for a long time, your fish is likely sick. It should also be noted that some tropical fish tend to shimmy to attract partners, which is a common activity. Nevertheless, it would help if you looked at the following aspects to ensure that nothing bad happens with your beloved pets.

Why Is My Fish Shaking?

Stress fish


Like humans, fish get stressed out as well. There are many causes that lead to stressful situations for your fish, such as pH fluctuations, ammonia levels, an unbalanced diet, or potential threats from aggressive fish. They are occasionally found hiding or swimming very fast and end up crashing into obstacles.

If this situation is neglected, your fish will weaken and eat less. Some fish even lose their colors and become more likely to catch diseases, possibly infecting other tank mates.

Dirty Water

When your tank is dirty, the water will be filled with dust and algae, which directly harm your fish’s well-being. Poor water quality can disrupt the water environment and lower the level of oxygen, thereby making your fish more aggressive and stressful.

Dirty water also increases the toxin level in your aquarium. Ammonia and nitrate contents are emitted from rotten leftovers and waste, including fish food, plants, and dead fish.

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Colder or hotter temperatures are just as troublesome for fish as for humans. For example, tropical fish wouldn’t be able to tolerate the cold weather of temperate regions and vice versa.

The main reason for temperature issues is tank heaters. If your heater stops working or you don’t have a heater at all, tropical fish will shimmy because of the cold. Excessive temperature will also affect their behavior; you wouldn’t want to boil them in the tank!

Another reason is transportation. Suppose your fish still shake when the temperature is right; likely, they have already been weakened before they were at the fish shop. The prolonged inadequate temperature in the vehicle in which they were transported to the fish store might be the cause.

Parasites & Infection

There is a good chance that your fish will catch diseases from unsanitized environments. They tend to shake themselves or rub their bodies against the wall to eliminate parasites or uncomfortable feelings. This could be dangerous for your fish’s health if not timely prevented.

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How To Help My Fish Stop Shaking?

How To Help My Fish Stop Shaking?

Adjusting Water

The first and foremost work to do is to ensure the ideal aquatic habitat for your little buddies. The best temperature range for most types of fish is between 72 to 78 degrees Fahrenheit or 22.5 to 25.5 degrees Celsius. 

Any temperature higher or lower than that can make your fish feel uncomfortable. Check your heater system from time to time.

You should also keep a large enough tank for your pets; the best tank size for a medium-sized school of mollies is 10 gallons or approximately 38 liters of water. It can be difficult to keep tabs on water conditions all the time, so consider purchasing an aquarium kit.

Don’t forget to change the water regularly!

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Environment Maintenance

Removing water toxins such as parasites or acidic levels is very important. If you have small fish bowls, keep them in a warm, insect-free room. You can use specific chemical aquarium kits for tanks, such as Epsom salt, to decrease the acid level of the water.

It’s advised to use a filter to get rid of all dust or waste from your fish. They would be happy to thrive in a clean, toxin-free tank; therefore, they would stop shimmying uncontrollably.

Reducing Stress

Fish should be treated like humans. To ensure the best care for your fish, keeping them in a healthy, stress-free environment is critical. In addition to improving the water environment, it paid to properly decorate and arrange decorations in your tank.

Don’t overload your aquarium with hordes of fish. Mollies enjoy swimming with their schools, so you should only keep a certain amount of mollies in a tank. You won’t want to introduce larger fish to your tanks of small fish, such as Discus and Angelfish.

The decoration is also part and parcel. Large rocks and plant bushes can be used as hiding or sleeping places for your fish, helping them feel safer in their habitat. If possible, try to install hidden pumps and water filters near the hiding spots to encourage them to live there.

Last but not least, feed your fish in the right amounts on time. Underfeeding will force your fish to fight over food while overfeeding pollutes your tank with leftovers. Consult fish shop owners about the right amount of food for your fish before buying.

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Final Verdict

Why is my fish shaking? We hope this article can answer the question. 

If you notice that your fish are constantly shimmying, you should check on the water condition first because the water environment is the most common reason for your fish’s struggle. 

Feel free to share this article with your fellow aquarium owners if you think it is helpful. Thank you for reading!

Alex is a pet freelance writer and editor with more than 10 years of experience. He attended Colorado State University, where he earned a Bachelor’s degree in Biology, which was where he first got some experience in animal nutrition. After graduating from University, Alex began sharing his knowledge as a freelance writer specializing in pets.

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