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Q&A: Why Is My Fish Swimming Against the Walls of the Tank?

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Dr. Mark is a veterinarian. He has been working with dogs for more than 40 years.

A too-small tank filled with dirty water may cause your fish to develop repetitive motions like glass surfing.

A too-small tank filled with dirty water may cause your fish to develop repetitive motions like glass surfing.

Why Is My Fish Swimming Along the Walls of the Tank?

"My fish keeps swimming against the walls of the tank and won't stop no matter what I do. I've tried using cardboard to cover the outer glass and putting my finger on the outside of the glass in front of it, so it would back away from the glass. What can I do?" —Laura

Poor Water Quality and Inadequate Tank Size

Some fish will develop repetitive motions just from being kept in a tiny tank, but the most common reason is that the water quality is poor. Goldfish produce even more waste than some tropicals and need a lot more water per fish and a good filtration system.

The most important step for your goldfish is to get a larger tank with a pump and filter. There are many causes of cloudy water, but the most common we see are fish kept in tiny aquariums without flowing water and filtration. The ammonia builds up, the pH changes, and water can become overgrown with bacteria and algae.

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There is a type of parasite that will cause fish to swim strangely, but I would take care of the water before worrying about that. A lot of used tanks are out there, and you can usually find a good deal so that your goldfish will be more comfortable. If you cannot afford a tank at the moment, at least get a little pump so that the water will flow a little.

When you get a new tank, be sure to get a proper lid for it, as the plastic wrap you are currently using isn't helping your fish's health either.

For more information about this issue, here's a great article about glass surfing that you may want to read.

This article is not meant to substitute for diagnosis, prognosis, treatment, prescription, or formal and individualized advice from your veterinarian. Animals exhibiting signs and symptoms of distress should be seen by a veterinarian immediately.

© 2022 Dr Mark

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