Why is Goldfish Staying at Top of the Tank?

Disclosure: I may earn a commission when you purchase through my affiliate links. As an Amazon Associate I earn from qualifying purchases. – read more

Goldfish are pretty standard options as tank fish, thanks to their hardiness, chill attitude, and gorgeous presence. They are also pretty easy to care for since they only require a clean environment, stable water parameters, and a varied and nutritious diet.

The only problem I could point out with goldfish is that they are extremely messy.

One of the reasons for that is that goldfish lack a stomach. Instead, they rely on their intestine to digest the food and extract the valuable nutrients as it passes through. So, they will easily produce more poop than other fish.

They also tend to overeat quite often, which can affect their digestive system and produce even more poop as a result.

These 2 characteristics are responsible for a variety of health problems, some of which can turn deadly fast.

So, when it comes to experiencing health issues, goldfish will showcase a variety of symptoms, usually growing in severity over time. However, at first, the most relevant sign is an erratic swimming pattern and overall activity.

It’s atypical to see goldfish swimming on their side, staying too long on the substrate, tipping upside-down, or spending too much time at the water’s surface.

What do these behaviors tell about their current state? Let’s see!

5 Reasons Goldfish Swim at Water Surface

Before diving into the topic, remember that neither of the following causes can be determined accurately simply by assessing the fish’s swimming pattern.

However, how the fish swims and moves through its environment serves as a great alarm signal, informing you that something’s not right with your goldfish.

That being said, here are the 5 primary reasons why goldfish insist on remaining at the water’s surface:

1. Stressed Goldfish

Goldfish can get stressed for a variety of reasons, including aggressive tank mates, improper diet, poor water conditions, too cold or too hot waters, too intense lights, etc.

All these problems will create a variety of other symptoms and health issues along the way. But initially, the goldfish will manifest its discomfort behaviorally by how it swims.

If you’ve determined that your goldfish is stressed, you should race to determine the cause.

Otherwise, the fish’s problems will only get deeper, as severe and prolonged stress in fish can cause:

  • Starvation – Stressed goldfish will also refuse food or, at best, display a low appetite. This will cause them to eat less than they should, risking starvation over time. Vitamin and mineral deficiencies are also real risks with potentially deadly effects.
  • Get sick – A stressed goldfish will soon experience a weaker immune system. This leaves the goldfish vulnerable to diseases, parasites, and bacterial infections, especially in suboptimal water parameters. It’s also worth noting that many goldfish already have a variety of intestinal parasites and pathogens in their system; many of these also swim freely in the tank’s water. These pathogens are kept under control by the fish’s immune system. When that safeguard mechanism fails, so will the fish’s health.
  • Infect other fish – A stressed goldfish with a weaker immune system will fall victim to various parasites that could spread to other tank inhabitants as well. Many of these pathogens will lead to deadly conditions like Ich, swim bladder disease, dropsy, or hole-in-the-head syndrome.

The upcoming points will detail some of the common stress triggers among goldfish and most fish in general.

2. Lack of Oxygen

This generally happens in poorly maintained environments that lack proper cleaning and aeration. It’s also an issue in overcrowded tanks, causing fish to compete over the available oxygen, in which case many will head to the water surface to breathe.

It’s not that they breathe atmospheric air, although some can do that like Bettas, but because the dissolved oxygen in the tank water is higher near the surface.

The same problem tends to occur in waters hotter than normal. Warm waters hold less oxygen than colder ones, and since goldfish are cold-water fish, you can see the problem.

You should keep your goldfish in water temperatures between 68 to 74 F. The more you go over the top threshold, the less oxygen the water will hold, increasing your goldfish’s risk of suffocation.

When that happens, your goldfish will display specific symptoms, including fast mouth and gill movements and spending more time at the water surface.

3. Inadequate Water Temperature

This is exactly what I’ve been mentioning previously. Warm waters will stress your fish since the dissolved level of oxygen will drop.

But cold waters will also stress them out. Typically, wild goldfish can withstand extremely cold waters, as they are even capable of entering a hibernation state during the winter.

This ability also carries over to slim-bodied goldfish, which are tank fish.

These haven’t been subjected to as much selective breeding as fancy goldfish, for instance, which means that their biology is much closer to their feral ancestors.

This is the main reason why slim-bodied goldfish are fit for that pond life, while fancy goldfish are not.

The latter is the exclusive result of selective breeding, so their genetic makeup isn’t as fit as other goldfish.

Don’t expect them to adapt to cold waters. While they can withstand some temperature variations, frequent or massive fluctuations will affect their immune system and cause lethargy, poor appetite, and unusual swimming behavior.

4. Ammonia and Nitrite Problem

This issue is more common in poorly maintained aquatic systems, and it’s more prominent in goldfish tanks. Goldfish are already famous for their messy nature, as they poop more often than other fish.

Not providing sufficient tank maintenance and skipping your weekly water changes too often will have dire consequences in the long term.

Residual food, dead matter, algae, and accumulated fish waste will poison the water, decrease oxygen, increase the harmful bacteria, and cause ammonia and nitrites to spike.

The latter is especially dangerous since both ammonia and nitrites are deadly chemicals that can wreak havoc in a close aquatic system.

A reliable filtering system will dilute ammonia, clear the water, and increase oxygenation, but it can’t work miracles.

You still need to undergo regular tank maintenance and partial water changes to stabilize the environment.

To counter and prevent ammonia buildup, remember to:

  • Avoid massive water changes – Only perform partial changes of up to 10-15% of the total water volume, preferably weekly. The frequency mostly depends on how large the tank is and the number of fish. Changing too much of the water at once can even produce the opposite effect of what’s expected. Large water changes will not only dilute the essential water minerals that your goldfish require to remain healthy but disturb or even destroy the tank’s beneficial biofilm as well. Without nitrifying bacteria, the system won’t be able to self-regulate, causing ammonia to spike immediately.
  • Prevent overfeeding – Overfeeding is a common problem in the tank world, but especially among goldfish, for 2 reasons. The first is that goldfish will eat as much food as they have. The second one is that they will transform it into poop. More food, more poop, more water pollution, and also more digestive problems. These are all linked to overfeeding. So, how do you prevent the problem? Feed your goldfish 2 times per day and only enough fish food for them to consume within 2-4 minutes. Anything more than that is excess.
  • Monitor ammonia and nitrites – A water tester kit is absolutely necessary for all fish tanks, especially goldfish. And especially when you have a large tank with a lot of goldfish pooping everywhere. I advise testing the water at least once or twice per week in case of crowded aquariums or whenever you observe unusual swimming behaviors. Detecting ammonia spikes in time will save your goldfish from ammonia poisoning, which is usually deadly.

5. Aggressive Tank Mates

This is another problem in the fish world that will almost always come with unexpected side effects. Goldfish are generally peaceful fish and don’t appreciate the company of aggressive, territorial, or overly curious fish species.

Even small and peaceful fish species like zebra danios can hurt goldfish due to their predilection toward nipping at their large and flashy fins.

Such behaviors will stress out the goldfish, causing them to retreat to their safe space. If they don’t have one, they will simply do their best to avoid the bully.

In many cases, this translates to spending more time at the water surface or near the substrate. This is generally a sign that the goldfish is stressed and needs a break.

In some rare cases, and if the bullying is severe, your goldfish may even jump out of the tank.

Which they have been observed to do on more than one occasion. So, either keep goldfish in single-species tanks or choose their tank mates carefully.

By the way, you can’t really rely on tank decorations and plants to provide goldfish with reliable hiding spots. When it comes to goldfish, tank decorations should be kept to a minimum.

Fancy goldfish usually have bulky bodies, large eyes, and even larger fins that can get injured in stiffer plants and rugger or sharp decorations.


Goldfish are quite resilient fish, which is why they’re rated among the most popular aquarium fish you can get.

But it’s not normal for goldfish to remain static for too long or stick to one area of the tank.

They usually roam the entire space available to them back and forth and display a dynamic and healthy behavior.

If your fish seems lethargic or showcases abnormal swimming patterns, investigate the situation more in-depth. You will thank yourself later.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
Leave a Comment

Your email address will not be published. Required fields are marked *