Do Harlequin Rasboras Like Current?

Harlequin Rasboras do not typically like much current, although they can handle a moderate flow of water and require some water movement to remain healthy and oxygenated. The flow from your tank’s filter (when set on low) should provide enough water movement to keep them happy and thriving. 

Harlequin rasboras are favorites in the tropical fish community as they are striking and easy to take care of. However, even they have their requirements. Read on for everything about the suitable current for harlequin rasboras, how to tell if the current is too strong, and what the dangers of this are.

Do Harlequin Rasboras Like Current?

Whether you’re thinking of purchasing your first harlequin rasboras, or are trying to modify a tank to suit them better, one of the first things you may wonder is how much current these little fish require. The answer is, very little!

Harlequin rasboras thrive in slow-to-moderate water movement and will not do well in fast currents. Thus, the slow flow from your tank’s filter will provide sufficient current for your harlequin rasboras to imitate the water flow they are accustomed to in the wild while keeping your tank clean.

What Is The Best Filter Setting For Harlequin Rasboras?

So, if harlequin rasboras like a flow filter setting and are uncomfortable in a rapid flow, what is considered slow to rapid flow, and how should you set your filter to best achieve it?

We recommend setting your filter at 5 to 10 turns per hour for small to medium tanks of harlequin rasboras. Putting your filter on this setting will provide them with enough water flow to remain happy and healthy but will ensure they do not feel buffeted by the current.

Aquarium Heater Next to with Single Amazon Sword and Hornwort

Why Don’t Harlequin Rasboras Like Current?

So, why don’t harlequin rasboras like current, and why is a gentler flow of water movement ideal for them?

Harlequin Rasboras naturally occur in slow-moving streams and peat swamps in Asian countries such as Malaysia, Singapore, and Thailand. As a result, they have not evolved to be resilient to fast-moving water or strong currents but rather to thrive in slow-moving, peaty water, which is full of vegetation.

Thus, a gentle current is best for harlequin rasboras in aquariums, as it mimics the slow-flowing streams in which they naturally occur.

We also recommend adding many plants to your harlequin rasbora tank and keeping the lighting dim, as both of these features mimic those of their natural habitats and thus will make your fish feel right at home!

How To Tell If The Current Is Too Strong For Harlequin Rasboras?

Living in water that is flowing too fast can be very bad for fish. It will cause health issues and may even result in eventual death. So, if harlequin rasboras dislike strong currents, how can one tell if the current inside their tank is too strong?

If you are concerned that the water flow in your harlequin rasbora’s tank is too intense, here are some indicators that you should be on the lookout for:

  • Your harlequin rasboras are struggling to swim. Harlequin rasboras are small fish, and so they are greatly affected by strong currents. If you see them struggling to swim or swimming very fast, the water flow in your tank is too fast.
  • Your harlequin rasboras are being washed off course. If your fish are managing to swim but can’t swim in a straight line, the current in their tank is too strong, and they are fighting to correct course when they swim.
  • Your harlequin rasboras are huddled in the corner of your tank. If you observe that your harlequin rasboras are bunched up in the corner of your tank and remaining relatively still while avoiding other areas of your tank, your current may be too fast.
  • Your harlequin rasboras are hiding. If your fish constantly hide in their vegetation or the objects in your tank, they may be too scared of the strongly flowing water to venture out into the tank.
  • If the water is too choppy, your water flow is too strong. If your water is visibly disturbed or choppy, the flow is far too strong for your harlequin rasboras and should be turned down immediately.

These are all common indications (although not guarantees) that the current in your tank may be too strong for your harlequin rasboras. If you are worried that this is the case, try reducing the filter settings to create a weaker flow.

Group of Harlequin Rasboras at Top of Tank

The Dangers Of A Fast Current For Harlequin Rasboras

Now that you know that the ideal current for your harlequin rasboras is very slow-moving, you may wonder what the dangers of fast-moving water are for them.

Water that flows too fast for harlequin rasboras may eventually lead to the death of these little fish and, if not, it is still associated with an extensive range of health problems, including:

  • Physical and psychological stress (which brings with it a range of health problems of its own)
  • Scale damage or torn fins
  • An inability to eat that results in weight loss

Small fish such as harlequin rasboras may even be sucked into the filter and trapped there if it is too strong, injuring and eventually killing them.

For these reasons, you must ensure your filter is not too strong in your harlequin rasboras’ tank. It is essential to address the issue timeously if you suspect the filter might be too strong, as doing so can save your fish’s lives.

Do Harlequin Rasboras Like Warm Water?

Now that you know the correct speed of water flow to ensure your harlequin rasboras flourish, you may be wondering about another element of your tank water, the best temperature for these fish. So, what is the proper water temperature for a tank of harlequin rasboras?

The ideal water temperature for harlequin rasboras is between 72- and 83 degrees Fahrenheit (23-28 degrees Celsius), with 76-80 degrees Fahrenheit being the best for spawning.

Harlequin rasboras thrive in this temperature water, as it mimics the temperature of their natural habitats in the streams of Asia. Thus, to ensure that your harlequin rasboras are living their best lives, aim to keep your tank water at a temperature of around 75 degrees Fahrenheit (24 degrees Celsius).


Harlequin rasboras originate from slow-moving swamps and streams and thus do not thrive in fast-moving water, which can be dangerous for them. Having too much current in your tank may even result in injury or death to these fish. A slow flow from your filter (set at 5 to 10 turns per hour) will thus provide sufficient water movement to keep your harlequin rasbora happy and healthy.