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Rainbowfish Care Sheet

Developed with and approved by a qualified veterinarian.

rainbow fish care sheet

Includes a variety of rainbowfish, including:

  • Celebes rainbow
  • Australian rainbow
  • Boesemani rainbow
  • Turquoise rainbow
  • New Guinea rainbow
  • Madagascar rainbow
  • Dwarf neon rainbow
  • Yellow rainbow
  • Threadfin rainbow



Scientific name: Marosatherina ladigesi, Melanotaenia splendida, Melanotaenia boesemani, Melanotaenia lacustris, Glossolepis incisus, Bedotia geayi, Melanotaenia praecox, Melanotaenia herbertaxelrodi, Iriatherina werneri 


Rainbows are a colorful group of freshwater fish consisting of more than 50 species originating in Australia, Madagascar, New Guinea and Sulawesi. Rainbowfish can be found in a variety of areas from rivers to swamps, but most of the species for the aquarium trade are captive-bred. These peaceful, schooling fish dwell in the middle to upper levels of the aquarium.


Typical appearance and behavior

  • Males and mature fish are generally more intensely colored
  • Most rainbowfish have compressed, elongated bodies with two dorsal fins
  • Juveniles of both sexes are often very different in color than adults and can appear like separate species
  • Rainbows are very active and require plenty of open swimming space
  • Rainbowfish are a schooling species and do their best in groups of five or more


Care Difficulty Beginner to intermediate, depending on species
Average Life Span Up to 8+ years with proper care, depending on species
Average Adult Size 2-6+ inches long, depending on species
Diet Omnivore
Minimum Habitat Size 10+ gallons, depending on species
Water Temperature 72-82°F




Habitat size

A minimum of 10 gallons is recommended for smaller-sized adult rainbowfish like threadfin, however, water conditions can change rapidly in smaller water volumes. A larger aquarium is recommended for larger adult species such as Boesemani.


Building your habitat

  • Water health - Provide proper filtration to help ensure optimal water quality and fish health. Moderate to strong water circulation, based on the species, should be provided to mimic water currents and high oxygen levels found in the rainbowfish’s natural habitat. Stable water quality (pH, ammonia, nitrate, nitrite) and water temperature are critical to the health of aquatic life. If you are unsure of your water quality, bring a sample to Petco for free testing. Ensure water temperature does not fluctuate more than +/-2 degrees direction in a 24-hour period.
  • Décor- Provide plants, rocks and caves  for hiding places and plenty of room for movement




What to feed your rainbowfish:

A well-balanced rainbowfish diet consists of:

Flakes, pellets, freeze-dried, frozen or live food

Feed a variety of food to ensure complete nutrition


Things to remember when feeding your rainbowfish:

  • Feed small amounts two to three times daily, no more than fish can eat in one to two minutes
  • Thaw frozen food before feeding


Rainbowfish care

Water care: Maintaining great water quality with regular water changes and adequate filtration is important to help keep your rainbowfish healthy

  • Daily: check filter, water temperature and other equipment
  • Weekly: check water quality at least once a week
  • Monthly: change 10 to 25% of the total volume of water every two to four weeks or as needed. Change filter media monthly

Avoid overcrowded conditions; they are a major cause of stress and disease


Where to buy


Various rainbowfish are available for purchase at your local Petco location. If visiting your local location, please call ahead to check availability




Tank mates

  • Tetras
  • Barbs
  • Mollies
  • Swordtails
  • Platies
  • Rasboras
  • Danios
  • Corydora catfish




Signs of a healthy  fish

  • Clear eyes
  • Healthy appetite
  • Bright, even coloring
  • Fins completely intact and undamaged
  • Free of parasites or disease


Red flags (If you notice any of these signs, contact your local aquatic specialist or veterinarian.)

  • Loss of color or appetite
  • Spots or fungus on body or mouth
  • Listlessness
  • Erratic swimming
  • Labored beathing
  • Elevated scales
  • Cloudy eyes or pop-eye
  • Weight loss
  • Bloating
  • Frayed or discolored fins

Common health issues

Health Issue Symptoms or Causes Suggested Action
Health IssueFin rot Symptoms or CausesFrayed or disintegrating fins; the base of the fins usually reddens. Suggested ActionImprove water quality; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueIch Symptoms or CausesWhite spots appear on fins and body; fish rubs against hard objects or swims erratically. Rapid respiration. Suggested ActionQuarantine fish immediately; add freshwater aquarium salt; use a commercial ich remedy as directed. Consult your local aquatic specialist or aquatic veterinarian.
Health IssueFungus Symptoms or CausesCloudy eyes, open sores and/or reddening of the skin. Suggested ActionImprove water quality; add aquarium salt; use a commercial antibacterial remedy as directed. Consult your local aquatic specialist or aquatic veterinarian.
Health IssueCottonmouth or columnaris Symptoms or CausesCottony white growths along the body and/or gills, frayed fins and gills turn brown and necrotic in late stages; caused by bacterial infection. Suggested ActionQuarantine fish; improve water quality; lower aquarium temperature to 72°F to deter bacteria from growing; medicate as directed; consult your local aquatic specialist or aquatic veterinarian for treatment.




  • What do rainbowfish eat? Rainbowfish benefit from a varied diet that includes flakes, pellets, freeze-dried food, and frozen or live food such as brine shrimp or bloodworms
  • What fish can live with rainbowfish? Rainbowfish can live with a variety of other fish, including tetras, barbs, mollies, swordtails, platies, rasboras, danios and corydora catfish
  • How big do rainbowfish get? Rainbowfish can grow up to 2 to 6-plus inches, depending on their species
  • Are rainbowfish friendly? Rainbowfish are typically peaceful community fish who prefer to swim in schools
  • Are rainbowfish fin nippers? Rainbowfish are generally shy and peaceful fish, however, some males may try to establish dominance if sharing a home with other males


Additional care sheets


Notes and resources

Ask a Pet Care Center associate about Petco's selection of products available for the care and happiness of your new pet. All products carry a 100% money-back guarantee.

Because all aquatic life are potential carriers of infectious diseases, such as atypical mycobacterium and salmonella, always wash your hands before and after handling your aquatic life and/or habitat contents to help prevent the potential spread of diseases.

Pregnant women, children under the age of 5, senior citizens and people with weakened immune systems should contact their physician before purchasing and/or caring for aquatic life and should consider not having aquatic life as a pet.

Go to for more information about aquatic life and disease.


Note: The information on this Care Sheet is not a substitute for veterinary care. If you need additional information, please refer to the sources on the following page or contact your veterinarian as appropriate.