How to Care for a Harlequin Rasbora

Select an aquarium large enough to accommodate your harlequin rasboras. These fish only achieve a maximum size around 2 inches, but because they require a great deal of swimming space, they should be kept in tanks 10 gallons or larger.

Keep your harlequin rasboras in groups with at least eight of their own species. These fish are a schooling species and will be less nervous and more active in large groups.

Line the bottom of your tank with at least 1 inch of dark sand or gravel substrate. Dark substrates will encourage your harlequin rasboras to show their best coloration.

Decorate your harlequin rasbora tank with live aquarium plants, large rocks and pieces of driftwood to mimic the natural habitat of these fishes. Concentrate tall plants and large decorations near the back and sides of the tank so there is plenty of open swimming space left in the middle.

Treat your aquarium water with a water conditioner to remove harmful toxins and chemicals like chlorine. Follow the instructions on the bottle to determine the proper dosage.

Install an aquarium heater in your tank to maintain a water temperature between 72 and 82 degrees Fahrenheit. Harlequin rasboras are tropical fish and may not thrive in water temperatures below 70 degrees Fahrenheit.

Use an aquarium filter to keep your tank water clean. Select a filter that provides both mechanical and chemical filtration to ensure the removal of both solid and dissolved wastes from your tank water.

Diffuse the lighting in your tank by adding some floating plants to the top of your tank. These plants will simulate the natural environment of the harlequin rasbora.

Add some dried leaf litter to your tank to further simulate the natural environment of these fishes. Harlequin rasboras come from a blackwater environment where the water is naturally stained by decaying plant matter.

Test your aquarium water chemistry once a week using an aquarium water test kit. Record the results in a journal so you have an idea what the "normal" levels for your tank are. This will help you spot problems with water chemistry before they have a chance to negatively impact your tank.

Feed your rasboras a varied diet of high-quality flakes or granules and small live foods like daphnia and artemia. Supplement the diet of your rasboras with freeze-dried bloodworms or tubifex worms and fresh vegetables.

Perform weekly 10 to 20 percent water changes in your harlequin rasbora tank to keep ammonia levels under control and to keep the tank water clear. Make a larger 25 percent water change once a month and replace your filter media at this time as well.