Harlequin Rasboras make good tank mates for Bettas.
Rasboras have a gentle nature that keeps them from agitating Bettas, and their fast and agile swimming keeps them safe from a Betta that is having a bad day.
Not all Rasboras, however, get along with Bettas as well as Harlequins.
Let’s begin by taking a closer look at the requirements of Bettas and Harlequin Rasboras in the same tank.
How Do Bettas and Harlequin Rasboras Look in the Same Tank?
Bettas come in many morphs and in a variety of brilliant colors. They like to be the star of the show.
In your aquarium, as in the wild, Bettas tend to live alone. A Betta grows to about 3 inches (75 mm) long.
Harlequin Rasboras only get to about 2/3 the size of Bettas. They grow to about 2 inches (50 mm) long.
Harlequin Rasboras also come in brilliant colors. They can be copper-orange, pale pink, or bright red.
They can have black or blue triangular markings on their backs.
There are also varieties of Harlequin Rasboras that have more of a copper or golden hue or a brilliant blue.
Importantly, Harlequin Rasboras don’t have flowing tails that seem to invite other fish to attack them.
And unlike Bettas, Harlequin Rasboras like to swim around with tank buddies. They usually form a shoal of six to eight fish, unlike the solitary Betta.
Water Conditions for Bettas and Harlequin Rasboras
Bettas and Harlequin Rasboras can be found in the same water in the wild. They both originate in slow-moving, quiet waterways in Southeast Asia.
This means that although every fish tank needs a filtration system, both Bettas and Harlequin Rasboras need to avoid a very strong flow.
Harlequin Rasboras like their water temperature between 73° and 82° F (23° and 28° C), while you can’t go wrong keeping the water for your Bettas at a constant 78° F (26° C).
Just keep the water at 78° F (26° C), and both Bettas and Harlequin Rasboras will be happy.
Harlequin Rasboras and Bettas both like the pH of their tank water around 6.8 or 6.9, slightly acidic.
They do well with a water hardness of 3 to 18 dGH. Scientists report that Rasboras can tolerate acidic, low-oxygen water, but this is never ideal for any fish.
All of this means you won’t have any problems adjusting the water in the tank to keep both kinds of fish happy.
Choosing and Decorating the Tank for Bettas and Harlequin Rasboras
Since you will be keeping up to eight Harlequin Rasboras in the same tank, they will need at least 20 gallons (80 liters) to swim in.
Even when you have a solitary Betta, it likes a sizable tank, also at least 20 gallons. A 55-gallon (220-liter) tank would be even better.
Choose a dark substrate to contrast the beautiful colors of both your Betta and your Harlequin Rasboras.
Put lots of lush vegetation along the back and sides of the tank to give your Harlequin Rasboras lots of hiding places.
If your Rasboras mate, they will use the vegetation for their bubble nests. Choosing a few plants with broad leaves will give your Betta a place to rest, too.
Bettas like to have a “cave” they can claim as their own. Resin clamshells are perfect for this purpose.
Don’t use real clamshells, because they leach calcium into the tank water, and give the water an unhealthy alkaline pH.
Bogwood makes both a good anchor for plants and a good hiding place for Bettas.
An artificial log of bogwood will provide a hollow interior just the right size for your Betta to rest in during the day or sleep in at night.
Bettas and Harlequin Rasboras prefer a long tank over a tall tank. Bettas like to “come up for air.”
Harlequin Rasboras like to swim around with their tank mates. These activities are easier in a tank that has more surface area.
Don’t forget to cover your tank. Both Bettas and Harlequin Rasboras are natural-born jumpers, and tend to escape if they are left alone.
What About Feeding Time?
When you keep Bettas and Harlequin Rasboras in the same tank, you will feed them at the same time.
But you won’t necessarily feed them the same food.
Bettas are carnivores. In the marshes, streams, and lakes of Southeast Asia where they originate, they mostly feed on tiny crustaceans, fly larvae, and water fleas (Daphnia) they catch at the surface.
Harlequin Rasboras are omnivores. They feed on a variety of plant and animal matter, including some of the same bugs that Bettas eat, and also worms and algae.
A good compromise diet for feeding both kinds of fish at the same time is a combination of pellet food, tropical fish flakes, and occasionally bloodworms or brine shrimp.
Offer a little blanched lettuce or spinach for your Harlequin Rasboras.
Your Betta will mostly feed at the surface, while your Harlequin Rasboras will clean up any little bits that sink down into the tank. Your Betta will eat its fill and then some.
For that reason, it is important to put out just enough food to last a minute or two. You don’t want your Betta to overeat, and you don’t want food to decay in the bottom of the tank.
Keeping Fish Diseases Under Control
Given good water quality and adequate food, both Bettas and Harlequin Rasboras are hardy fish.
They don’t get sick very often. However, you should not put them in the same tank straight from the store.
Keep fish in quarantine for at least two weeks after you buy them.
As a practical matter, you can quarantine all of your Harlequin Rasboras together in their eventual home, but you will need to keep your Betta in its own temporary tank to make sure none of your fish gets sick before you put them in all together.
Wash in any new toys or decorations in scalding hot water and allow them to cool off before putting them in the tank.
Don’t use soap or antiseptic, because they won’t come off completely. Wash any new plants in warm tap water before you set them out in the tank.
You can also help keep all of your fish healthy by keeping your filtration system in good working order, and by testing for ammonia and nitrites every week.
What About Putting Other Kinds of Rasboras in the Same Tank with Your Betta?
It’s not particularly hard to keep Harlequin Rasboras and Bettas together, but what about the other kinds of Bettas?
Let’s consider them individually.
Chili Rasboras, also known as Mosquito Rasboras, are tiny fish. Even when they are three or four years old, they will be just 0.8 of an inch (20 mm) long.
They swim together in greater numbers than the larger Harlequin Rasboras. You will usually keep at least eight or 10 of them in the same tank.
Because Chili Rasboras find protection in numbers, they need to be in a tank of 20 gallons (80 liters) or more.
And because a hungry Betta might try to eat them, they need lots of vegetation and hiding places.
Don’t expect them to share a cave with your Betta.
Chili Rasboras aren’t the best choice for keeping with a Betta, but they are beautiful fish.
If you decide to keep your Betta and Chili Rasboras together, give them lots of dim lighting and places to hide.
Scissortail Rasboras are on the large side for Rasboras. At 3.5 inches (88 mm) long, they may be bigger than your Betta.
They also like to shoal, so you will need to keep at least Scissortail Rasboras together in the same tank.
They need a tank of at least 20 gallons (80 liters), although bigger is better.
Scissortail Rasboras aren’t going to be intimidated by a Betta. Fortunately, because of their peaceful nature, they are going to be aggressive toward your Betta, either.
However, Scissortails are very fussy about water quality, so it is always better to add a Betta to your Scissortail tank than it is to add Scissortails to your Betta tank.
Keep Scissortail Rasboras in any tank where they have become established.
Lambchop Rasboras grow to be about 1.2 inches (30 mm) long. Their males are especially brightly colored.
And they become very active at feeding time.
They don’t injure each other when they feed, but they need a longer feeding time than other Rasboras, about three minutes, because of their feeding rituals.
Lambchop Rasboras are not quite as compatible with Bettas as Harlequins.
However, if you take good care of them, and you make sure you have at least eight or 10 Rasboras in their shoal, they won’t be harmed.
Dwarf Rasboras are tiny fish, no more than 0.8 inches (20 mm) long when they are fully grown.
They aren’t especially flashy, but they are interesting pets because they respond to the pigments in their food.
You can feed them in ways that bring out their full coloration.
Dwarf Rasboras aren’t a great choice for living with a Betta.
Even in groups of 10 or 12, they are easily intimidated by the Betta, and putting them together would cause your Dwarf Rasboras constant stress.
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