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Why Is My Cory Catfish Swimming Up and Down? (7 Reasons)

Why Is My Cory Catfish Swimming Up and Down? (7 Reasons)

This post is written to the author's best knowledge and is not intended to be used in place of veterinary advice. In addtion, this post may contain affiliate links. As an Amazon Associate I earn from qualifying purchases.

Many people love spending time observing their fish. It can be a lot of fun to sit and watch your fish as they swim around in the tank.

Cory catfish are excellent fish that you might have as part of a community aquarium. These fish are very popular due to being so peaceful.

They’re great community tank fish and it should be simple enough to keep them happy in your fish tank. It might be alarming when the fish start acting strangely, though.

Have you noticed the cory catfish swimming up and down the glass of the tank as of late? Why would they want to do this?

Is swimming up and down the tank a sign that there is a problem? Continue reading to get all of the pertinent information that will help you to care for your fish.

Cory Catfish Glass Surfing

When fish start swimming up and down the glass of the aquarium, it’s referred to as “glass surfing.” Glass surfing is something that fish do when they are stressed or somehow unhappy in the fish tank.

There might be many different reasons why your cory catfish has decided to start doing this. You’ll want to try to figure out what is wrong in the fish tank so that you can get things back to normal.

Below, you’re going to learn about many things that can cause cory catfish to act this way. You’ll be able to compare the information with what is going on in your fish tank.

It should make it easier to determine what is wrong. Once you understand the problem, you’ll be able to fix things and help the cory catfish to feel more at ease in the aquarium.

1 – Glass Surfing When First Introduced to a Tank

Catfish Glass Surfing

Glass surfing is very common when fish are first introduced to a tank. If it has only been a few days or weeks since you introduced the fish to the tank, then it might not be anything to worry about.

Being put in a new fish tank can be a stressful experience for a fish. It can cause them to feel stressed, and they might start swimming up and down the glass as a result.

Eventually, the cory catfish should start to feel more comfortable. If you’re feeding the fish well and you’re monitoring the water parameters properly, then the fish will start to feel better.

If the problem persists, then it’s a sign that something isn’t right. You’ll need to keep paying attention to see what the problem is.

2 – Water Parameter Issues

Water parameter issues are the most likely cause of glass surfing. Often, cory catfish will start to swim up and down the fish tank when they get stressed due to improper water parameters.

It’s also important to understand that water parameter issues can refer to many different things. There could be many different problems that will negatively impact water quality.

Not cleaning the fish tank often enough can cause spikes in the ammonia, nitrate, and nitrite levels. High nitrate levels have the potential to kill cory catfish very easily.

You need to clean the fish tank and do weekly water changes to keep things safe for the fish. Aside from this, you need to regularly test the pH balance.

The pH balance can be thrown off by various factors. Too many fish in the tank can produce too much poop, and that will throw the balance off.

Regularly check the pH balance to keep things in the right range for the fish. Cory catfish need the pH balance to remain between 7.0 and 8.0 and the alkalinity of the water should stay between 3 and 10 dKH.

Water temperature is important as well. Cory catfish can’t tolerate water temperatures that are too hot.

Generally, cory catfish will want water temperatures to stay between 74 degrees Fahrenheit and 80 degrees Fahrenheit. Specific types of cory catfish might have slightly different preferences, but this range will be a good general target when caring for any cory catfish.

3 – Cory Catfish Like to Live in Groups

Group of Cory Catfish

Another thing to understand is that cory catfish need to be kept in groups. It’s recommended to keep at least five cory catfish in the fish tank if you want them to feel comfortable.

Some enthusiasts even say that five will be too few fish. You might want to buy six or seven cory catfish for the aquarium.

If you only have two or three of these fish in the tank, then they might feel uncomfortable. The glass surfing can be seen as the fish making an effort to leave the tank to find better waters.

Many don’t know this, but cory catfish will die if they feel really lonely. If you were to try to keep one cory catfish by itself, it likely wouldn’t survive that long.

These are fish that live in schools and like being with their own kind. They can live happily in community tanks as well, but they do need a certain number of their own kind in the tank to feel okay with everything.

Try to get more fish for the tank to see if you can improve things. Of course, you need to have a big enough fish tank to keep the fish happy.

Many people make the mistake of keeping cory catfish in very small tanks because they aren’t that big. Since you’re going to need many of these fish, it’d be better to go with a slightly larger tank.

A 29-gallon fish tank should give you good results. If you’re going for a community fish tank, then you might want something larger depending on how many fish you wish to add.

4 – Incompatible Tank Mates

It’s true that cory catfish are peaceful fish that make excellent community fish tank members. However, these fish are not going to be compatible with just any freshwater fish.

Some fish might bother the cory catfish and cause them problems. You might have made the mistake of putting the cory catfish in aquariums with fish that they aren’t compatible with.

The glass surfing could be a sign that the cory catfish wants to escape. It’d be prudent to double-check to ensure that all of the fish in the community tank are compatible.

Cory catfish are compatible with many fish. Just ensure that the fish are compatible ahead of time by doing the necessary research.

5 – Issues with Food

Mottled Corydora Eating in a Fish Tank

Have you thought about whether the cory catfish are happy with their food? You might not be feeding the fish as well as you should be.

When fish aren’t happy with the food that they’re being given, it won’t be unusual for them to start glass surfing. They might be hoping to find different food.

Even giving fish the same food too much can make them unhappy. It’s better to vary the diet of the fish a bit.

Cory catfish aren’t picky about what they eat since they’re omnivores. Just make sure that you’re feeding them well and that you’re giving them recommended foods that meet their nutritional needs.

Since cory catfish are bottom feeders, you’re going to want to give them sinking nutritional pellets and algae rounds. They will also enjoy eating shrimp pellets as well as other foods.

6 – Overcrowded Fish Tank

A fish tank being overcrowded will be very negative for these fish. For the most part, cory catfish stay at the bottom of the tank and leave other fish alone.

When a fish tank has too many fish in it, it’ll be hard for the cory catfish to feel comfortable. The other fish are likely going to have issues, too.

Make sure that you’re not overcrowding the tank. Only put as many fish as you can comfortably fit in the fish tank.

Consider the amount of space that these fish need to thrive. It’d be better to get a second tank than it would be to try to cram too many fish into one aquarium.

7 – Lack of Hiding Spots

Cory Catfish Behind Plants

Cory catfish like being able to hide in the fish tank. If your fish tank doesn’t have good hiding spots for them, then they might feel uncomfortable.

This lack of comfort can lead to issues such as glass surfing. You should ensure that you have aquatic plants and other hiding spots for the fish in the tank.

Pick out good aquatic plants that the cory catfish will like. This will make it so that they can hide when they feel they want to.

You should notice less glass surfing once you add hiding spots to the tank. If you have no hiding spots for the fish right now, then that very well could be the issue.

Cory Catfish Darting in Spirals

When these fish start darting in spirals, it’s an indication that the ammonia levels are too high in the tank. Immediately check the ammonia levels and change things if they’re out of safe ranges.

You need to keep a close eye on water parameters to prevent such issues.

Cory Catfish Darting to Surface

Seeing a cory catfish dart to the surface will be normal. These fish gulp air from the surface and use it to get the oxygen that they can send to the rest of their body.

You’ll see the fish dart to the surface for a quick gulp of air before going back down to the bottom of the tank. This is normal and is not something to worry about.

Final Thoughts

Now that you’ve learned that cory catfish swimming up and down the tank is a bad sign, it’ll be possible to try to turn things around. These fish can become stressed for many different reasons, and the stress is what causes them to act this way.

It could be that the water quality in the tank isn’t good enough. They might not be getting enough food or you could be keeping them in groups that are too small.

Examine the situation in the tank and then consider what you can do to change things for the better. Your fish should stop glass surfing once you determine the problem and take steps to fix it.