Dwarf rasbora - Boraras maculatus

Dwarf rasbora - Picture by JJphoto.dk

Common name: Dwarf rasbora, Spotted rasbora
Scientific name: Boraras maculatus
Synonyms: Rasbora maculate, Boraras maculata
Size: 2.5 cm / 1 inch
pH: 4.5-6.5
Temperature: 75 - 79°F/24 - 26°C
Hardness: 1 - 5°H
Lifespan:  3-5 years

The Dwarf rasbora is a very peaceful species. It is a shoaling fish that always should be kept in groups of 8 fish or more. Larger shoals will result in more colorful and active fish. Dwarf rasbora is not suitable for community aquarium due to its very timid nature and small size. It will get stressed when kept with most other species. It is however suitable for aquariums with other very small and timid fish species and shrimps. The Dwarf rasbora is an excellent choice for aquascaped tanks where plants play the most important part.

The Dwarf or Spotted rasbora originates from South Eastern Asia where it is found in Thailand, Peninsular Malaysia, and Singapore. There are also (less reliable) reports of this species being present on Borneo and Sumatra. It is widely distributed in Peninsular Malaysia while the other countries have more limited populations. Different populations from different countries have different colorations and patterns.

In the wild, the Dwarf rasbora inhabits black water streams and rivers connected to peat swamps. It lives along fallen leaves and braches in dark water (the dark colour is caused by tannins). The water in these areas is usually very soft and very acidic. They are often found in areas that have a pH-value as low as 4.0. The habitat of this species is threatened by human development and farming.

The Dwarf rasbora can be sensitive to changes in water conditions it is therefore important to allow acclimatization to take some time. This is true regardless of whether you just bough them or are moving them between aquariums at home.

Aquarium & care

The Dwarf rasbora can be kept in rather small aquariums. A 6 gallon / 30 L tank is enough for a small to medium sized shoal. The aquarium should be densely planted with floating plants on the surface to dim the light. You should also use bogwood and rocks to created shaded areas in which the Dwarf rasboras can seek shelter from the light and hide when frightened. Adding aquarium safe leaves on the bottom gives the fish more hiding places and creates a habitat more like the ones where they live in the wild. Leaves will also increase the chance of fry surviving in the holding tank. The bottom substrate is preferably dark soft sand. Filtration can be kept to a minimum.

The Dwarf rasbora is a black water fish and appreciates if the bogwood and leaves stain the water with tannins. The water can be filtered through peat to increase tannin levels in the water and make the tank more similar to their natural habitat. Simulating their natural habitat will make the rasboras display more vibrant colors.

It is important that the tank is well established before adding this sensitive fish.

Feeding Dwarf Rasbora

Dwarf rasboras are predators feeding on very small prey but they will easily adapt to accept flake food in aquariums. Flake food can be used as the basis for their diet but they need to be fed a varied diet including different types of live and frozen food as well to do well and show their best colours. A varied diet with a lot of frozen and live food is required to breed this species. Make sure to choose food that is small enough to suit this small species.

Sexing Dwarf Rasbora

Sexing Dwarf rasbora is not that hard. The females have rounder bellies and are (usually but not always) larger than males. The males show more intense colouring. This is especially true for dominant males.

Breeding Dwarf Rasbora

The Dwarf rasbora is not easy to breed in aquaria but not impossible either. It is a continuously spawning species where the female fish scatters a few eggs every day. They do not tend to their young. The fact that they lay a few eggs each day makes them ideal for permanent breeding aquariums; aquariums that have been designed to allow as many fry as possible to survive with the parents still in the tank. A few fry might survive in a well decorated aquarium even if no special concern has been taken to create a setup suitable for permanent breeding.

Dwarf rasboras can also be breed in a more conventional way. Breeding them the conventional way produces more fry but also requires more work than a permanent breeding tank.

If you want to breed the Dwarf rasbora the ”conventional way” you need an aquarium that is no smaller than 2 gallon / 8 L (3 gallon / 12 L is better). The pH-value is best kept between 5 and 6, although up to 6.5 usually works. The water hardness should be below 5.

You will not need any filter but if you want to use one you should choose one that isn’t too strong. An air pump sponge filter is perfect. The bottom of the tank should be covered with mesh or similar to protect the eggs from the parents; something that the eggs can fall through to fall out of reach from hungry adults. Plastic grass tiles are known to work as an alternative to mesh. You should also add some fine leafed plants like java moss to the setup to make the adult fish feel more secure and to offer them a spawning medium.

Once the aquarium is setup and the water parameters correct it is time to add two or three pairs of Dwarf rasbora to the tank. The pairs should be left in the tank for a couple of days and then be removed. The fry are very small and will need to be feed infusorians. They are usually large enough to accept newly hatched brine shrimp after 7-10 days and about a week after that they are usually large enough to accept mashed flake food. Do not perform water changes during the first two weeks as this can be to big a shock for the fry. This means that it is very important not to overfeed, since over feeding makes it difficult to maintain a high water quality.