6 Facts About Rainbowfish

By PetMD Editorial on Sep. 27, 2016

By Vanessa Voltolina

Whether you’re a lifetime lover of fish, or hope to work a pet fish into your current lifestyle, they can be beautiful additions to any home. Rainbowfish in particular are a popular type to keep as pets and, despite their ubiquity, the average pet parent may not know all that much about them. We’ve pulled together a few fun facts about rainbowfish to help you get better acquainted with these finned friends and learn how to care for them.

Fact #1: What’s in a Name?

If you say you own rainbowfish, it’s unfortunately not a very specific identifier. “There are a large number of [rainbowfish] species,” said Kristin Claricoates, DVM at Chicago Exotics Animal Hospital. Although there are more than 50 species of rainbowfish, neon dwarf rainbowfish, salmon red rainbowfish, Madagascar rainbowfish and threadfin rainbowfish are some common species found in the pet industry.

Fact #2: Their Color Enhances with Age

As the name rainbowfish implies, these fish come in amazing iridescent colorations that change when the light reflects, be it a shiny silver or a blue and yellow combination. What you may not realize, though, is that “the color of a rainbowfish develops as the fish grows older, and is at its brightest when [the fish is] stressed, or when competing for the attention of a female,” said Claricoates. However, a stressed fish is not a happy or healthy fish.

Outside of their pretty colors, having more than one male rainbowfish in your tank means that they may become aggressive towards each other and can injure each other during breeding season. Limit male rainbowfish to one per tank, and opt to fill your tank with other beautiful aquatic creatures. Additionally, when you purchase your rainbowfish, be sure to ask the pet store or breeder what the sex of the fish is (particularly before you put them with other fish in a tank). It is fairly easy to determine the gender of a rainbowfish, although it can be more difficult when they are young.

Fact #3: Rainbowfish Want to be Schooled

Unlike some fish that are better off solo, rainbowfish can live with other fish, and prefer to be in schools of five or more, said Claricoates. While limiting male rainbowfish, as mentioned above, may seem unfortunate, the good news is that these fish do fairly well with others, including tetras, discus, guppies and other female rainbowfish.

Claricoates suggests providing your fish with several hiding spots in their tank, just in case things get stressful, and utilizing real or artificial plants (artificial plants are easier to maintain), and larger rocks that can be cleaned. The use of these components “makes the tank feel a bit more like a natural environment for these fish,” she said.


Fact #4: Rainbowfish Need Freshwater Environments

Over 80 percent of the known species of rainbowfish are found in New Guinea, usually in lakes or tributaries, said Claricoates. “What this means in a tank is that the water should be freshwater [that is dechlorinated],” she said. She also recommended a canister filter, which is a thorough way of keeping tank water relatively clean. It can be a bit more expensive, she said, but it’s an investment to make the tank a better environment for your rainbowfish.

In addition to providing your rainbowfish with a freshwater environment, the ideal temperature of your fish tank should be around the midpoint of 72 to 86 degrees Fahrenheit, which can be monitored with a tank thermometer, said Claricoates. The pH of your water should be between six and seven, ideally about 6.8, with nitrites and ammonia at 0 ppm, she said. Fish do not have a strong immune system, and the quality of the water in the tank is one of the barriers you can provide to them to keep them healthy. “pH changes can make them more susceptible to illness, or even death,” said Claricoates.

Measuring the nitrates and ammonia in the water are important, as elevated levels are indicative of waste and fishes’ byproducts. “If they are high, it often indicates a dirty tank, and can create health issues for your fish,” she said. “Routinely do water quality checks to ensure the ideal health of your fish,” she said. Water checks can be done by fish stores for you on a monthly basis or you can purchase a home kit to test your water, she said.

Fact #5: Make “Tank Changes” a Habit

Tank changes — or cleaning the tank and its flora, as well as refreshing the water —should be done regularly. Claricoates recommended replacing one-third of the tank water once weekly. As changes in water temperature (even by as little as one degree) may stress your fish, she recommended normalizing the temperature of the water you are adding by filling a two-gallon jug with tap water, adding de-chlorinator per the package instructions, and leaving it at room temperature for a day before adding it to your tank.

“Using a siphoning tube will help you get the debris from the bottom of the tank,” she said. “I typically prefer no substrate at the bottom of my tank unless deciding upon natural plants.” She notes that the addition of plants and snails in a tank increase the risk of parasite problems in fish, “so unless you plan on regular check-ups by a vet or parasite treatment for your tank, you may not want to tackle this challenge.”

Fact #6: Portion Control Equals Better Health

Overfeeding fish is the number one cause of problems in fish aquariums, she said. As a general rule, if food falls to the bottom of the aquarium, you are overfeeding your fish. Excess food food in the tank will also make your tank dirty and can cause an imbalance of water parameters, Claricoates said.

She said that feeding rainbowfish a balanced, flake-food diet daily is key, but only as much as the fish can easily eat within five to ten minutes of the tank feeding. 

Image: EEO via Shutterstock 

Help us make PetMD better

Was this article helpful?

Get Instant Vet Help Via Chat or Video. Connect with a Vet. Chewy Health