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The Glowlight Rasbora (Microrasbora sp. thuzari")

Read on the breeding methods for the glowlight rasbora or Microrasbora sp. thuzari

By Mike Hellweg |

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Glowlight rasbora
Glowlight Rasboras by Gary Lange

In recent years, there has been an explosion of new species coming from Myanmar, the nation formerly known as Burma. Many of these new species are not only new to the hobby, but they are also completely new to science. Among these finds have been several species of Cyprinids of the genera Danio and Microrasbora, and some of their close cousins. All are small tropical fish that are ideal candidates for aquarium life. The glowlight rasbora reaches about 1½ inches when full grown.

Males and females are similarly colored. Male have a pattern similar to cardinal tetras, except the cardinals’ bright blue stripe is replaced with a luminous powder blue stripe, and the red is replaced with a bright rusty orange color. Both sexes sport a small black spot at the front of the anal fin just above the urogenital pore.

Because scientists have yet to officially recognize these fish, I have elected to include their scientific name in quotes. In the trade, they are usually listed as Microrasbora sp. “thuzari.” Microrasbora might be correct because they are similar in general appearance to Microrasbora rubescens. I have also seen these fish listed as Rasborathuzari” and Devario sondhii, but they lack the diagnostic spot behind the operculum of D. sondhii. Some speculate that there may be a new Devario species closely related to D. sondhii. Talk about confusing!

The origin of the glowlight rasbora is debatable. Like the collectors of some of the new tropical fish coming from Myanmar, glowlight rasboras’ collectors guard their secret collecting spots. This is understandable, but it can make things difficult for us. We have no idea of the water parameters where these beauties are found. Many blackwater areas exist in Myanmar, but there are also brackish coastal waters and hard water areas further inland.

Glowlight rasboras are easy to care for. Even though the water parameters of their wild habitat are unknown, in captivity they are very adaptable. I’ve kept mine in tap water with a pH of about 7.2 and a total hardness of 125 ppm. I keep the temperature in my fish room about 78 degrees Fahrenheit, so the water in their aquarium is usually about 74 to 76 degrees Fahrenheit. I perform a 50-percent water change every week and use a sponge filter.

Like their Danio cousins, glowlight rasboras spend most of their time schooling and chasing one another. They must be kept in decent-sized groups because without tankmates, they simply languish in the corners and slowly decline. However, in a group of their own they shine. Five or six would be the smallest group, though a group of a dozen or more is a spectacular sight.

Give them a long, low aquarium with lots of plants along the sides and back and an open area in the front for swimming. Provide them with good lighting and a current. A power filter or powerhead is appreciated, and you will often see them swimming into the current created by them. If using a sponge filter, keep it bubbling high.

When it comes to feeding, these fish will eat flake, tiny pellet, freeze-dried, frozen and live foods. I feed a basic diet of finely ground mixed high-quality flake and newly hatched brine shrimp. The flake food I use is a mix of several different types of flake. The blend consists of Spirulina, veggie, shrimp, earthworm, and color and plankton flakes. I grind them between my fingers before feeding to make them small enough for the fish to eat in one bite. I use a mortar and pestle to grind up freeze-dried and frozen foods before feeding smaller tropical fish such as the glowlight rasboras.

If given a good diet, proper water changes and water movement, it won’t be long before they start spawning. They will spawn in the community aquarium, but none of the eggs will survive because other tropical fish will eat them. If you really want to raise fry, you will have to take a few extra steps.

Set up a 5- to 10-gallon aquarium with water from the same source as your main aquarium. Add a sponge filter and a couple of clumps of plants, but don’t put anything on the bottom. Move the female here for seven to 10 days, and leave the male in the main aquarium. Feed both the female and male diets rich in quality live foods, along with some high quality frozen or freeze-dried foods like bloodworms and krill. After seven to 10 days, you will notice the female bulging and male with bright colors. You are now ready for the next step.

Give the female aquarium a good cleaning, removing every scrap from the bottom. Then add a mat or grid to the bottom of the aquarium. You can make a spawning grid from needlepoint canvas, which you can get in the craft department of most major craft stores. Make sure the holes are at least 11/2 mm across, because the eggs are about 1 mm and you want them to fall through. You also want enough room to ensure a tight fit and a slight upward bulge. Add a couple of clumps of plants, Java Moss works well. Yarn mops are also acceptable. Rinse them well, and lay them on the bottom of the aquarium over the spawning grid.

Add the male in the evening before you turn the lights off. A good idea is to set the aquarium in a room where it will be exposed to some indirect early morning light. This is an excellent trigger for spawning. If all goes well, you should witness spawning in the morning. The male and female will chase each other around the aquarium, separate, move into or over the plants or mop, quiver together and release eggs into the plants. The eggs are not very adhesive and usually fall through to the grid, where they pass safely to the bottom of the aquarium where the adults can’t get them.

After the spawning is done, remove the adults, and slow the filter to a gentle bubbling. Shake off the plants, mops and mat, and remove them. The eggs will be covering the bottom. Then it’s time to wait. The eggs hatch in two to three days. The fry will resemble small dark hairs with eyes and bulging bellies. They will hang on the lower edge of the glass all around the aquarium. A few days later, they will begin making their first attempts at swimming. After one day, they should be swimming in the water column.

Then it is time to start feeding. The fry will need tiny foods. The best first foods are things such as infusoria, paramecia and other microscopic life. You can also feed a commercial fry food made especially for egg-layers. Follow the directions on the package carefully, and don’t overfeed. It’s a good idea to add snails to the aquarium to help clean uneaten food. For best growth, perform a small water change daily. Do this by siphoning uneaten food and waste from the bottom of the aquarium with a piece of rigid airline tubing attached to a long piece of airline tubing. This will help you avoid sucking up fry. Take the makeup water from the adult aquarium because it is more stable. Do water changes on the adult aquarium more frequently to make up for the water you are removing each day.

When they reach about a week in age, the fry are large enough to move on to newly hatched brine shrimp. One way to tell if they are eating is that their bellies will be bulging and bright orange. Feed them at least twice daily. As the fry grow, you will need to separate them into larger quarters and eventually find them new homes. The glowlight rasbora is a beautiful tropical fish, so you should have no trouble finding a shop that will take them in trade.

If you reach this point, congratulations! You’ve just had another successful Adventure in Fish Breeding.

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Reader Comments

Jozsi    Edmonton, AB

8/12/2009 7:58:26 PM

Hi there I just purchased a group of twelve rasbora rubescens and they are quite colorful I have them in with zebra danios and white clouds a lovely picture.

Zach    Stow, MA

11/28/2007 2:36:44 PM

cool fish :)

Lee    Pleasant Valley, NV

11/21/2007 8:14:10 AM

What a beautiful little fish, appreciate the picture. Thanks for the in-depth on breeding, perhaps we will give it a try in the future.

Ben    Irvine, CA

5/17/2007 8:18:08 AM

This is a great article. Very fact filled and accurate. Thanks for the great info!!

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