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What it Means if Your Fish is Swimming Erratically

fish in aquarium

Fish make beautiful pets that absolutely keep us entertained, but when their swimming habits change or become erratic it can cause us to wonder: “Is that normal?” Fish swimming in circles, up and down, backward and other consistent swim patterns are among the behaviors you may observe of your aquatic life at some point, and understanding them will help you know when things are perfectly normal, and when there is cause for concern.

Signs and symptoms of your fish swimming erratically

The behavior: Rubbing or banging against items in their tank
What it could mean: If you’ve noticed that your fish seems to be rubbing or banging against things in their aquarium frequently, they could be displaying what’s known as “flashing,” or “itchy fish.” As the name implies, a fish that’s constantly banging up against things in their aquarium could actually be trying to scratch themselves. There are a number of reasons they could be displaying this behavior, but the most common is parasites. If your fish is flashing, check for tiny white specks on your fish, which is the classic symptom of a parasite known as Ich. Both freshwater and saltwater fish can get this parasite —which is similar to fleas in mammals—and they can be very irritating.
Gill or skin flukes, a wormlike parasite, may also cause similar erratic swimming behavior but can be harder to spot. A fading in your fish's color or change in the appearance of their gills—such as excessive visible mucus—can be indications of skin or gill flukes.

If you notice what you believe to be behavior that’s indicative of Ich or flukes, contact a veterinarian who specializes in aquatic life for advice on treatment, which often entails a combination of over-the-counter remedies and quarantine (for Ich) or natural remedies (for flukes).
The behavior: Your fish is swimming erratically.
What it could mean: It’s not uncommon for fish to swim erratically—fast and seemingly in no particular configuration or for an apparent purpose. However, if you begin to notice a pattern, it could indicate poor water quality in your tank. Common water quality issues in home aquariums include incorrect pH levels (the appropriate level varies from species to species, but usually a pH level between 6.8-7.5 is ideal for freshwater and 8 - 8.4 for marine life), ammonia buildup, high amounts of nitrates or nitrites or temperature changes. The water quality in your tank can change quickly, so regular water tests are essential. If your fish is being medicated, it’s important to test your water more frequently, since some treatments can impact the aquarium’s bacteria colonies and cause a change.
The behavior: Your fish is swimming upside down or on their side
What it could mean: If your fish has started swimming upside down or on their side, this could be a sign that they are suffering from something called swim bladder disease. When this occurs, a fish is unable to regulate the air that’s going in and out of their swim bladder and may swim either upside down or on their side in an attempt to regulate it. Swim bladder disease is fairly common in goldfish, and although the name implies that it’s one particular health issue, this “disease” is actually just the symptom, which can be caused by a number of different things. If you think your fish is suffering from swim bladder disease, discuss treatments with your veterinarian or an aquatics care specialist, since over-the-counter treatments are generally effective in helping solve the problem.
The behavior: You notice your fish continually swimming in circles
What it could mean: Although some circular movement is normal, a fish—and particularly a goldfish—that is constantly swimming in circles—especially in a rapid, darting motion—could have ammonia poisoning. Ammonia poisoning can happen in an aquarium when ammonia and nitrite, which are poisonous to fish, builds up in the water. Immediate treatments for ammonia poisoning are to stop feeding your fish (so as not to add to additional ammonia buildup) and to perform small, frequent water changes, while ensuring that it’s being properly aerated with either an air pump or water pump. Test the water frequently for ammonia buildup—levels should be at or near 0 ppm for both nitrites and ammonia—and then you can begin to feed your fish again.
If you have questions about your fish’s behavior—or about the proper setup of your aquarium to allow for the maximum health and safety of your fish—stop into your local Petco and talk to an aquatics specialist who can walk you through everything you need to know to care for your aquatic life and aquarium.

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