Exclamation Point Rasbora (Boraras urophthalmoides)

The Exclamation Point Rasbora is a very hardy and peaceful fish but does not fair well with community fish due to its small size and rather timid nature. It will do best when maintained alone, with similar sized fish or other miniature species. This Rasbora also makes an ideal companion for shy anabantoids and are perfect for the nano or planted aquarium.

This Rasbora is a shoaling fish by nature and ideally should be kept in a group of at least 8-10 specimens. Sustaining it in decent numbers will not only make the fish less apprehensive but will result in a more powerful, natural-looking display. Males will also present their best colour and some exciting behaviours as they compete with one other for female attention.

Their body usually is golden yellow with a dark green or brown lateral stripe flowing down both sides of the body, ending just behind the dorsal fin. Some populations can develop an intense orangey-red line above the dark lateral stripe when in good condition.

There is also a similarly coloured distinct round dark blotch on the caudal peduncle. The darker patterns resemble a horizontal exclamation mark.

Habitat

The Exclamation Point Rasbora has been found in Sai Buri, Mae Klong and Chao Phraya river basins in southern peninsular in Thailand where they inhabit shallow water structures such as marshes, swamps, ponds, rice paddies and peat bogs. The water is usually very soft and acidic and sometimes stained a tea-colour from tannins.

This fish has also been recorded in both Cambodia and Vietnam where one unusual group inhabits the moats and ponds of the Angkor Wat temple complex near Siem Reap.

You will find that in all the following areas there is an abundance of dense aquatic vegetation.

Other Rasboras of interest

Diet & Feeding

In the home aquarium, these fish will accept dried foods of a suitable size such as micropellets and crushed flake food but should not be given these solely.

Daily meals of small live and frozen foods such as artemia, baby brine shrimp, daphnia, cyclops and mini bloodworm will result in the best colourations and also encourage the fish to come into breeding condition.

Breeding

Like many Rasboras, this species is an egg-scattering, non-stop spawner that exhibits zero parental care. In the presence of both females and males exceedingly small numbers of eggs can be laid daily. In a well-furnished, mature aquarium, it is consequently viable that small numbers of fry may also begin to show up without human intervention.

However, if you want to raise the number of fry, the fish will require a slightly more controlled approach. You can still condition the adult group together, but you should also set up a separate tank. This tank should be very dimly lit with the bottom either left bare or covered with some mesh with significant enough holes so that any eggs that fail to stick to the plants can pass through but small enough so that the adults cannot get to them. The broadly available artificial grass matting can also be used and works very well.

The water itself should be slightly acidic with the temperature being somewhat higher than usual. A good size clump of Java moss or other fine-leaved plants should also be placed in the tank taking up about half the available space. Filtration is not necessary, but if you like, you can use a small, air-powered sponge filter.

You should then introduce two or three pairs of well-conditioned adult fish into the tank. It is sensible to make the transfer slowly to avoid extreme levels of stress, but if conditions are to their liking, they should begin to spawn the next morning.

While this species unquestionably consumes their eggs, they do not seem to appear to seek for them as other small cyprinids do actively. Once spawning has begun, it should continue daily. The pairs should be kept in the tank for no more than a couple of days before removing them as the first eggs should start to hatch by the second day after the original spawning.

The tiny babies will survive on their yolk sacs for around 24 hours or so after which they will require infusoria, paramecium or other microscopic food. About a week or so later the fry should be big enough to accept foods like nauplii, artemia and microworm. As the days progress, the additional babies should start to appear from later spawning results.

It would be best to wait a week or two before performing small water changes to avoid unnecessarily shocking the young fry.

You may enjoy the following profiles