How to Tell if Water Current is Too Strong for Fish?

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Are you worried that the water current in your aquarium may be too intense for your fish? You’ve come to the right place because I’ll give you all the necessary information to determine if the water current is too strong for your fish.

Remember that not all fish are the same. Some may thrive in faster-moving currents, while others only accept slower-moving currents.

Do you know what happens if the water current is too strong for fish? They may not die immediately, but it will negatively impact their health. In many cases, you won’t even need to replace your filter to reduce the current water speed!

I’ll teach you how to spot these symptoms in your fish and how to reduce the water current in your aquarium.

Keep reading to find out more about this.

Do Aquarium Fish Like Strong Current?

Every fish species is different in terms of appearance, diet, behavior, resilience, and so on. One significant difference between aquarium fish is their acclimatization to the water current.

Some fish are perfectly fine in a fast-moving current because they’re stronger. In contrast, others are only comfortable in a slow-moving current. These fish tend to be smaller and weaker.

The answer to your question: “Do aquarium fish like strong currents?” is “It depends on the fish.” Tetras, for instance, come from rivers and streams where the water is constantly moving.

They won’t have any problems adapting to a faster-moving water current. You can crank your filter up without having to worry about tetras, in other words.

On the other hand, Bettas have evolved in slow-moving bodies of water. Their natural habitat consists of slow-moving streams, stagnant ponds, rice paddies, and marshes.

So, they’re more likely to be affected by the fast water current in the aquarium than other fish.

Pay close attention to their behavior and watch for any symptoms of stress because they’ll die if you don’t remedy the situation.

A good rule of thumb is to use a fish tank filter only to oxygenate the aquarium and keep it free from debris.

Anything else is irrelevant and might put your fish’s life at risk. Don’t actively try to impose a fast water current on your fish, thinking that it might do them good. It won’t.

In fact, even fish living in fast-moving bodies of water will sometimes find places of hiding to rest.

How do You Know if Water Current is Too Strong?

Are your fish cramped up in the corner of the aquarium and remain relatively stationary for most of the time?

Do you see them “flying” through the aquarium when they try to move around? Did you notice any fin or scale damage on some of your fish? Some of your fish may also refuse to eat, and you don’t know why.

This might be why. These are some of the things to look for when you suspect the water current is too strong for your fish.

It might sound to be common sense but try not to crank your water filter to maximum power.

No fish species “needs” that much water circulation speed. Even if the fish species is native to fast water streams, they have no issues living in slower-moving bodies of water.

And if you have a mixed aquarium, you have even more reasons to keep a neutral water circulation speed.

Watch out for these things when you suspect that the water current is too strong:

  • Your fish can’t swim in a straight line. This might be because the current pushes them in random directions, and they must swim against it. Or, the current is too strong, and the fish are looking for areas with lower current speed;
  • The fish doesn’t swim with ease. Is your fish struggling to swim through the aquarium, making large movements, and swimming in random directions? Or does he appear to be blown away by the water? This might be because the water current is too strong;
  • The fish is constantly hiding. If your fish is trying to hide among the decorations in the tank, it might mean the water current is too fast. The fish wants a place to relax and stay still, so it’ll look for hiding spots where the water current is slower;
  • The fish is actively avoiding some areas in the tank. If you notice that your fish doesn’t go to some areas of the tank, the water current might be too strong there.

While these factors don’t necessarily point to a strong water current, they might. It’s worth lowering the water circulation speed to see if the fish exhibit the same behavior as before. If they don’t, great job.

If they have the same behavior, it means something else is bugging your fish. It means the water current wasn’t too strong.

What Happens if Current Is Too Strong for Fish?

Read below if you’re wondering what happens to the fish if the water current is too strong in the aquarium.

I’ve compiled a list of all the possible symptoms your fish may exhibit if the current is too strong for them:

– Stress and Health Problems

If your fish has to fight against the water current, it will become stressed. And we all know how dangerous stress is for fish.

It can even kill them if the stress continues unabated. Health problems can also occur if the fish refuses to eat because of the stress.

Stressed fish also become more vulnerable to disease. If you bring a sick fish into the aquarium, stressed fish are more likely to fall ill as well.

Healthy fish, on the other hand, may not get sick because they’re less vulnerable. So, you see why ensuring that your fish aren’t stressed is very important.

Many fish refuse to reproduce and may stay hidden for long periods when they are stressed.

Eventually, the stress will kill them if you don’t do anything about it. It might seem like there’s no apparent cause for their death, but there is.

– Fish are Unable to Eat

If the water current is too strong, your fish may refuse to eat. Having to fight against the current to eat could be too difficult for them.

If the fish are small and weak, they’ll be physically exhausted and unable to eat due to the strong water current. And even if they can fight against it, they will become stressed.

When fish don’t eat for extended periods, they will become sick and eventually die.

Healthy fish may go without food for 1-2 weeks but not longer. And if your fish is stressed, they become ill so they won’t survive without food for 1-2 weeks.

Most likely, they’ll die sooner than that.

– Fin or Scale Damage

The fish may damage their fins or scales when trying to swim against the current. Or, the water current is so strong that it throws the fish against the aquarium walls or the decorations inside.

If that happens, the fish’s fins or scales may be ruptured or damaged severely enough that it leads to death.

If it doesn’t lead to death, the fish will be even less vulnerable to the water current because they can’t swim properly.

The stress will build up, and they may fall sick, refuse to eat, and eventually die.

Or, they’ll constantly hide in the corner of the aquarium because they can’t fight against the current with a wounded fin or scale.

– Difficulty Swimming

When your aquarium fish start having difficulties swimming, it might be because of the strong water current. Please pay attention to their behavior when swimming.

Do they appear to exert much effort yet can’t move very fast? Do they seem to be blown away at times? They can’t swim in a straight line for too long, and they resort to swimming diagonally or turning back?

That’s because the water current is too strong. Some fish have weaker bodies and lower physical capabilities. If your filter is cranked up to max, I guarantee you fish won’t feel too good about it.

They’ll start swimming erratically, break their fins or scales, and eventually fall sick and die.

– Fish Staying in One Spot

Lastly, you may notice that your fish are cramped up in the same spot in the aquarium. This might be a corner of the aquarium or a hiding spot where there are a lot of decorations hiding them.

If you notice this, chances are the water current is too strong. The fish are staying as far away as possible from the source of their discomfort, which is the filter.

How to Reduce Flow Rate on Your Filter?

To reduce the flow rate of your filter, simply adjust the flow from the filter itself. However, this is only possible if you have an adjustable filter.

If you don’t have one, how about buying one? If that’s not possible, then you might want to buy a pre-filter sponge and wrap it around the nozzle of your filter.

This will slow down the flow rate, and the water current will be more bearable for your fish.

Here are other solutions you can try to reduce the flow rate of your filter:

  • Use decorations to slow the water flow – you can use things like plants, driftwood, or artificial caves to let the fish rest and hide from the current. While this isn’t ideal, it still reduces the stress on the fish;
  • Add some rocks or a layer of gravel to the filter media. This will act as an obstacle that reduces the flow of water enough, so the fish aren’t stressed or exhausted;
  • Place a large decorative element in front of the filter’s nozzle. This way, the initial burst of water will be spread around and become less intense;
  • Buy a new adjustable filter. If you can adjust the flow of water, then you’ll solve the problem in a few seconds.

It’s not difficult to reduce the flow rate on your filter if you know what you’re doing. You can even create a filter baffle by using a plastic bottle.

Please measure the length of the filter, cut the bottle until it matches the filter’s size, and then attach it to the filter. This will slow down the water current significantly.


To summarize, your filter may be the cause of stressed, sick, or dying fish in your tank. If the water current is too strong, the fish become agitated and stressed, they may damage their fins and scales, refuse to eat, and become sick.

The symptoms become apparent once you pay close attention to their behavior.

Fortunately, it’s pretty easy to slow down the flow rate of your filter, either through conventional or unconventional means.

I recommend buying an adjustable filter or a pre-filter sponge to slow down the water current. I’ve used them myself, and I had no more problems with strong water currents in my tank.

If you have any questions about this topic, feel free to comment below!

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.
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