Dwarf Rasbora (Boraras maculatus): Ultimate Care Guide


Dwarf Rasbora are small shoaling fish that are native to slow-moving blackwater environments in Southeast Asia. These timid fish are best suited to a species-specific aquarium, since they can be easily stressed when living with other incompatible species. If they are to be placed with other species, tank mates should be selected with caution. Other small fish with similar temperament, such as other Rasbora species may be a good choice.

Dwarf Rasbora are sensitive to water quality changes and are best kept by moderately experienced hobbyists. As this is a shoaling species it prefers to live in groups of 8 or more. Kept singly, it is likely to become stressed and susceptible to disease.

Native to blackwater environments, Dwarf Rasbora will thrive in very acidic water with decomposing plant matter. An ideal environment includes lots of plants and rocks to provide hiding spaces. Tannin content in water can be boosted with bog-wood and catappa leaves. A big benefit to using catappa leaves is during breeding: Dwarf Rasbora fry will feed from biofilms that form on the leaves as they decompose.

Dwarf Rasbora Care

Dwarf Rasbora are sensitive to water quality changes. This makes them more susceptible to disease when receiving inattentive care. They do best in a high quality environment, including enough plant growth.

How many Dwarf Rasbora should be kept together?

A shoaling species, Dwarf Rasbora should be kept in groups of 8 or more. This species should not be kept in small groups or singly. Without a group to shoal with they will become stressed and more susceptible to disease.

Dwarf Rasbora (Boraras maculatus)
Dwarf Rasbora (Boraras maculatus)

Dwarf Rasbora Temperature

Dwarf Rasbora prefer temperature in a range of 75° – 79° F (24° – 26° C).

Dwarf Rasbora Water pH

Dwarf Rasbora are native to blackwater environments and will need acidic to very acidic water in a range of 4.5 – 6.5 pH.

Dwarf Rasbora Size

Dwarf Rasbora are a small fish reaching a maximum size of 1 inch. In an aquarium the average length when mature is 0.8 inches.

Dwarf Rasbora Food & Diet

Dwarf Rasboras are predatory carnivores and will eat a wide range of fresh or frozen meaty foods such as Tubifex, bloodworms and baby brine shrimp. Mysis shrimp, common in marine aquariums are also a good choice. Some pellet food can be used as long as it will sink slowly or float. Dwarf Rasbora swim in mid to top levels in the water column and prefer to feed in those areas.

It can be a good idea to cultivate your own live food for this species. Brine shrimp are the easiest. Daphnia is a nutritious choice but can be a challenge to raise.

Dwarf Rasbora should be fed two to three times a day. Only feed what can be completely consumed in three to five minutes. This species is sensitive to water quality. Avoid having uneaten food rotting in their tank.

Dwarf Rasbora Lifespan

Dwarf Rasboras will live roughly 3 to 5 years with expert care. To ensure the maximum lifespan provide a well planted tank and a nutrient rich diet of meaty foods. Stress can be a problem for this species. Whether this comes from not enough plants or being harassed by other fish, it can lead to disease and lower life expectancy.

Dwarf Rasbora Tank Size

Dwarf Rasbora are smaller fish and are ideal in smaller aquarium setups. A 5 gallon aquarium can support a shoal of 8 individuals. A general rule of thumb is to allow for an extra 2 gallons for every shoal member beyond this. So a 10 gallon tank can support a shoal of 10, or possibly 11 members.

Tanks should be wider than they are tall. This species wants horizontal swimming space. Larger tank base measurements are also useful during spawning. Males will claim an area of “floor space” and become territorial. This behavior is less of a problem in a wider tank.

Tank Setup

Dwarf Rasbora want dense planting and dimmer, shaded light. Substrate choice should be darker sand or soil that can buffer acidity and provide color contrast. Bog wood can also help increase water tannin content and will give this fish places to hide. Another way to increase tannin is by introducing catappa leaves. These leaves are popular with blackwater enthusiasts. They will leach tannin and other useful compounds before sinking and decaying. Decaying leaves will mimic this fish’s natural environment and can host biofilms which can be eaten by newly hatched fry.

This species is accustomed to slow moving waters. Filtration should not be strong enough to make excessive currents. Even a loud bubbler can annoy these timid fish.

One method to increase acidity is by introducing peat moss or prepared peat pellets. In larger tanks this can be added to the filter, but this is not a great idea with Dwarf Rasbora tanks. Why? Because it can quickly get out of control, releasing too much tannin and increasing acidity to dangerous levels. For smaller tanks there are two alternative methods: First, you can soak the peat with aquarium water in a separate container for a few days. This water can be strained and added to your tank as needed. A second method is placing some peat in a stocking or cloth infusion bag with a rock. Tie the bag up and place it in the tank. As it sits in the water it will reduce pH and add tannin. A good amount of peat to start with is 3 or 4 grams per gallon. If you decide to experiment with either of these methods you’ll need to watch water quality closely.

Planting will need some extra attention. Dwarf Rasbora are more relaxed and happier in heavily planted aquariums. Plus, they are carnivores and won’t disturb any tank plants. But they also need dimmer lighting. Plants will need to be selected that can tolerate lower light levels. Java Fern is one excellent choice. Duckweed is another. Duckweed will also provide the shaded lighting this species loves.

As with all heavily planted aquariums, Co2 levels can be a concern. Co2 injection will aid plant growth and it can also lower pH. Since Dwarf Rasbora prefer more acidic water they can tolerate Co2 injection well. Just make sure levels don’t raise too high as it can suffocate your fish. It is difficult to maintain heavily planted aquariums without Co2 injection. Consider if this is something you want to add to your setup.

Remember that Dwarf Rasbora are sensitive to water quality changes. It is best to only add these fish to somewhat established tanks. New tanks can have variations that can kill this species. Start with some tank mates first for a few months before adding any Dwarf Rasbora.

Dwarf Rasbora Breeding

Dwarf Rasbora can be difficult to breed. They are egg scatters and will eat their own eggs. Prepare to remove plants containing eggs or use a separate breeding tank.

A breeding tank can be slightly smaller than usual. A 3 gallon tank will handle two or three breeding pairs. This tank should be outfitted with DIY or purchased spawning mops to catch eggs and a sponge filter.

Once the pairs have adjusted to the new tank, begin feeding live foods and increasing water temperature gradually to 79° F. After a few weeks the males will increase their coloration and females will fill with eggs. Males will start mating displays to attract a female. Females will scatter up to 50 eggs among the spawning mops during the breeding period. After this, remove the parents so they don’t eat the eggs.

Fry will hatch after 3 days and are free-swimming after 24 hours. Feed Dwarf Rasbora fry infuroria or liquid fry food. You can begin feeding freshly hatched baby brine shrimp after 10 days.

Dwarf Rasbora Male and Female

Dwarf Rasbora coloration varies by population. Males often have stronger colors and are slimmer. Females have less distinct colors and are plumper. During spawning, males will increase coloration and females will plump with eggs.

Common Diseases

Dwarf Rasbora can be susceptible to disease, particularly if they are stressed. Make sure they have well planted tanks and peaceful tank mates to keep them relaxed and happy.

Ich is a common ailment. White spots will form over the body and can rapidly spread to the entire tank if not treated quickly.

Swim Bladder disease is a bacterial infection that impacts the fish’s swimming ability and buoyancy.

Due to this species’ susceptibility to disease it is a good procedure to have a quarantine tank available. Some medications can’t be used on all fish species. Infected fish should be treated in a separate tank.

Many of these diseases are the result of bad water quality. Keep a regular water change schedule to reduce the likelihood of your tank becoming infected.

Dwarf Rasbora Tank Mates

Dwarf Rasbora are hard fish to pair with tank mates. They can be harassed by many larger species. They are naturally timid and can become scared even when there isn’t a real threat. The best choices are other small and slow moving fish. Guppys or Danios can be good selections. Shrimp, snails and small types of catfish can be good tank mates as well.

Dwarf Rasbora and Betta fish

Some Rasbora types can be good tank mates for a Betta, but use caution with Dwarf Rasbora. They are so small they can be intimidated by a feisty Betta. It is a paring that can work but watch them closely.

Dwarf Rasbora and Cherry Shrimp

Dwarf Rasbora are a great match with mature Cherry Shrimp. Cherry Shrimp will scavenge uneaten food and keep the water cleaner. A big benefit for the sensitive Dwarf Rasbora.

Where can I find Dwarf Rasbora for sale?

Dwarf Rasbora can be hard to find in local fish stores. Your best choices are Internet sources. This fish can be bought for around $5 USD per fish.

Dwarf Rasbora vs Chili Rasbora

Dwarf Rasbora and Chili Rasbora share many traits including size, shoaling behavior, timidness and care requirements. The Chili has more pointed fins and more prominent red coloration in some cases. If you are deciding which to add to an aquarium the decision will come down to which fish’s look you prefer. An aquarium setup for one will suit the other.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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