Fish are seemingly simple and straightforward creatures. They only have a small environment to spend their entire lives. Goldfish will randomly dart around the tank or seem to do all kinds of abnormal movements. They commonly like swimming in circles, up and down, or sinking to the bottom and laying there for a while.

Although you don’t typically have to be overly concerned, swimming erratically can also be your fish’s way of communicating that there is a problem in their little world.

In this article, you will learn about the six most common reasons that goldfish begin to swim more erratically.divider1- goldfish

6 Reasons Your Fish Could Be Swimming Abnormally

Glass Surfing


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Glass surfing is typically when a fish begins to swim up and down the glass. Some call this pacing as well since they might swim along the glass from side to side.

Often, this is an emotional response to their environment. The fish are trying to say that they feel stressed or something in their environment makes them unhappy.

If you notice this behavior continues for several days, try changing things in their environment to calm them down. If you have recently introduced something new, assume it wasn’t a hit and take it out to see if there is a difference in their behavior.

This response often has more to do with inappropriate tank mate choices, overstocking, or a tank size that is too small for the fish. Even something like the water pH and temperature might be driving them up the wall — pun intended.

Tank stress is one of the major causes of premature death for aquarium fish. Working out what causes their new stress is essential to ensuring their longevity.

Ammonia Poisoning


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If your fish begins to swim frantically in a consistent manner, especially if it is jerking and darting, they could be suffering from ammonia poisoning. Rapid circling with tucked fins is another vital sign. If it is a very severe case, then you will see ammonia burns turning black on your fish.

Other symptoms of ammonia poisoning include:
  • Rapid breathing
  • Gasping
  • Lethargy

Ammonia and nitrites are toxic to fish, and you should keep these levels as close to 0 parts per million (ppm) as you possibly can. Ammonia gets released into the tank as a by-product of rotting fish waste and food. It is a common issue with overstocked tanks.

Keeping a clean substrate and rotating your water are excellent ways to keep  ammonia levels down .

If you catch an ammonia issue from a fish’s reaction, treat it by halting your feeding schedule for a while. Aerate the tank heavily. Doing so helps fish breathe easier since ammonia in the water stops fish from breathing oxygen.

From here, do a water change and clean the tank. Afterward, test for ammonia and repeat until the levels are as close as possible to 0 ppm.

Swim Bladder Disease


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A fish’s swim bladder regulates its buoyancy. Typically, their swim bladder problems will result in them sinking to the bottom or floating to the top of the tank and not moving.

Swim bladder disease is not one specific ailment but can result from various issues that impact the organ. The disorder is most common among goldfish and bettas.

Since all kinds of possible issues can impact the swim bladder, multiple sources could be at fault for the problem. Overfeeding is one of them. Feeding your fish too much leads to constipation and will cause them to gulp air, ultimately causing the disorder.

Another common cause of this disease is improper water temperature. Know the best temperature for the fish species that your tank contains and keep the water temperature balanced. Keeping your tank clean is also essential.

External Parasite

Goldfish in freshwater aquarium_luckypic_shutterstock

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Perhaps your fish is doing all kinds of erratic movements, but they seem to always direct them towards some of the rougher materials in the tank. If your fish appears to rub itself against objects within their tank or bang themselves against the side, scraping at their scales or fins, it could be a sign they have an external parasite.

Examine their scales carefully since these parasites are generally relatively easy to spot. If there is anything there, invest in a parasite treatment from any pet store to treat them immediately.

Gill or skin flukes are worm-like parasites that are more difficult to detect than other external parasites. They cause your fish’s color to fade or their appearance to change, often with excessive mucus when it is severe.

Whirling Fish Disease

Goldfish in aquarium with green plants_dien_shutterstock

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Whirling fish disease is another one caused by a parasite. In this case, it is the Myxobolus cerebralis. The infection is typical among fish in the salmon family but can also be common in fish that live in aquariums, like your goldfish.

Researching the breeder or online store from which you buy your fish is one of the better ways to avoid fish that suffer from this disease. Infected fish swirl around in a corkscrew-type pattern and convulsive movements, breathing quickly and jerking backward. These symptoms generally occur between 35 to 80 days after they become infected.

It is common for fish to get infected with this parasite when fed the other primary host, oligochaete worms, or tubifex. They are commonly used in breeding production when the goal is to provide fish with a cheap source of protein.

There is not a lot that you can do if your fish becomes infected. Sometimes, their bodies will eventually expel the parasite, but it often results in nerve damage and skeletal issues later if they do not die.

Playing Detective

Finally, we want to end on a positive note. Fish are somewhat mysterious creatures. Swimming erratically doesn’t always mean that there is anything wrong. Swimming in circles or jerking around could be a form of play. Some species are particularly investigative and will use their detective skills by trolling all over the tank in odd ways.

Keep your goldfish’s tank clean, with plenty of aeration, and buy them from reputable sources. These are the best ways to keep them healthy for the long-term.

Featured image credit: HUANSHENG XU, Shutterstock