What Different Behaviors Mean in Freshwater and Tropical Fish

Have you ever wondered about unusual behaviors of your freshwater or tropical fish?

For a budding aquarist, your fishes' strange behaviors can be the subject of confusion and concern.

Picture this: One day you walk over to your aquarium and find one of your tropical fish floating belly-up at the top of the water. Upset, you open up the lid to retrieve your seemingly dead friend. But just as you do, the fish suddenly springs to life and darts away down into the aquarium.

What does this behavior mean?

To fully understand, care for, and enjoy your aquarium, it’s important to learn about the behaviors of your livestock. Here’s a primer on the basics of fish behaviors and what they might mean.

Picture of ballooned blow fish, a type of tropical fish.

Fish can sometimes exhibit unusual behavior.

Reproductive and Social Behavior

Some mating behaviors that fish exhibit might strike you as odd the first time you see them.

Indeed, many fish species have unique and unusual mating rituals. Among tropical fish, bonefish have been recently discovered to swirl like a tornado in their mating ceremonies. While African electric fish play “duets” by exchanging bursts of electric signals.

Among freshwater fish, the male drummer fish produces grunting and rumbling that sounds like drumming to entice the female, and betta fish perform an intricate dance just before mating. Whatever species you have, they too may display seemingly unusual behaviors that can be explained by courtship rituals.

But not all of them are so bizarre. Often, males build and defend nests as they enter mating seasons, even when chemically castrated. Pheromones released by females can excite them as well. Even in the absence of females, male fish are still driven to reproduce. These instinctual drives can result in more aggressive behavior than you might be used to seeing.

If you are breeding your fish, you should learn about what their pre-spawning, spawning, and post-spawning behavior patterns. That way, you’ll know what to expect. For example, does your species of fish maintain pairing after spawning while waiting for eggs to hatch?  Or do the temporary pairs immediately split up? Knowing these things can quell any worries you might have. Plus, it makes monitoring progress significantly easier.

Picture of an orange and purple tropical fish.

Some fish species "play dead" to fool other fish.

Playing Dead

There are other fish behaviors that can catch you off guard. Some are harmless, while  others require you to  do more maintenance to prevent illness.

Let’s revisit the example of the fish playing dead. Some species play dead to fool other fish, often targeting scavengers as a food source. The Central American cichlid is a perfect example.

However, in other species, this kind of behavior might also hint at a health issue. For example, with goldfish floating to the top of the water upside down might indicate either a digestive issue or a case of dropsy. Often, it’s caused by fish swallowing too much air when swimming to the top for their food.

Luckily, there’s an easy remedy for this. Thaw some frozen peas, skin them, mash the insides into manageable bites, and feed this to the fish. It should clear up the digestive issue, which you can then manage by feeding from the bottom or a few inches below the surface. If none of this helps, you may want to treat your fish for dropsy.

Image of a Tropical Fish (clown fish) hiding in a sea anemone

Your fish need enough hiding places to make them feel safe.

Unusual Swimming and Health Issues

Many fish naturally swim erratically during play or exercise. But this could also be the result of bad water quality. So, you should run tests to see if that’s the case.

Lethargic, listless behavior can also be the result of water quality. But this is usually caused by improper temperatures or overfeeding.

Gasping for air at the top of the tank can be indicative of poor water quality. Test your water in this case and consider an aerator for your aquarium.

Sitting at the bottom of the tank for a long time is normal for many species. Some spend all their time eating, sleeping, and swimming near the bottom. Others seem inactive during the daytime because they are nocturnal. But if this behavior starts suddenly, it may be the result of a disease like a swim bladder infection, which occurs due to poor water quality or diet.

There are also protective behaviors which fish adopt when they are still adjusting to environmental changes. For example, when you first introduce a fish to the aquarium, or after you’ve made changes to the layout, conditions, or inhabitants of the aquarium, you might notice the fish hiding. This is normal, and most fish become less shy as they grow comfortable.

Sometimes, you might notice fish showing more aggression. In this case, you should make sure your tank is large enough for the number of inhabitants and has enough hiding space. You might also quarantining fish before adding them to the tank, changing up scenery to break up claims over territory, and keeping a variety of fish so they aren’t competing to fill the same role in the ecosystem.

What to Do if Your Freshwater or Tropical Fish Acts Weird

There are all sorts of other behaviors that your livestock might adopt, and numerous reasons for those behaviors. Tropical fish, for example, might start standing strange due to the salinity of the water being off.

Unfortunately, unlike with many kinds of animals, you probably aren’t able to simply bring your fish to a vet. You’re largely on your own when it comes to health issues. You can research the species, read about diseases and other potential causes, and consult community forums online, but the information is somewhat scattered.

In such cases, it’s good to have an expert you can reach out to. Here at Living Art Aquatics, we have exactly the expertise you need. For 20 years, we’ve been the premier provider for professional aquarium design and exotic fish care in McHenry County, Illinois. So, if you have questions about the behaviors of your freshwater fish or tropical fish give us a call at (847) 737-5151.

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