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Cardinal Fish

Cardinal Fish

includes several cardinal fish species

Cardinal Fish have two distinct dorsal fins and can be found around the world. These slowmoving nocturnal fish make excellent additions to large community aquariums. Most species are recommended for beginning marine aquarists.

Cardinal Fish

Cardinal Fish Facts

Average Adult Size 2 1/2 to 5+ inches long, depending on species
Average Life Span depends on species
Diet omnivore
Minimum Aquarium Size 5+ gallons, depending on species
Water Temperature: 72-82°F
Salinity Level: 1.020-1.025


A well-balanced cardinalfish diet consists of:

  • Flakes, pellets, and frozen food.
  • Vary diet to ensure proper nutritional balance.


Things to remember when feeding your Cardinal Fish:

  • Depending on species and size, feed small amounts 2 to 3 times daily, no more than fish will eat in 1 to 2 minutes.
  • Thaw frozen food before feeding.


  • Keep in an appropriately sized aquarium; provide plants, rock and décor for hiding places and plenty of room for movement.
  • Stable water quality and parameters are critical to the health of aquatic life. If you are unsure of your water quality, Petco provides free water testing.

Normal Behavior

  • Peaceful, some species can be kept in small groups; different species should not be mixed.
  • Although nocturnal (active at night), cardinalfish can become used to daytime feeding and activity.
  • May become aggressive toward individuals of the same species; should be kept in groups of five or more.

Habitat Maintenance

  • Daily: Check filter, water temperature, specific gravity and other equipment.
  • Weekly: Check water quality at least once a week.
  • Monthly: Change 10 to 25% of the total volume of water every 2-4 weeks, or as needed. Introduce new inhabitants to the aquarium gradually.


  • Compatible with dwarf angelfish, blennies, clownfish and gobies. Can be compatible with large angelfish, damselfish, groupers, psuedochromis, tangs and wrasses.
  • May become aggressive in an overcrowded aquarium.


Signs of a Healthy Fish

  • Clear eyes
  • Eats vigorously
  • Fins completely intact and undamaged

Avoid overcrowded conditions; they are a major cause of stress and disease. Maintain good water quality with regular water changes and adequate filtration.

Red Flags

  • loss of color or appetite
  • spots or fungus on body or mouth
  • listlessness
  • labored respiration
  • weight loss
  • cloudy eyes
  • erratic swimming
  • frayed fins

If you notice any of these signs, contact your veterinarian.

Common Health Issues

Health Issue Symptoms or Causes Suggested Action
Health Issue Fin rot Symptoms or Causes Frayed or disintegrating fins; the base of the fins usually reddens. Suggested Action Improve water quality; consult your aquatic veterinarian for treatment.
Health Issue Marine ich Symptoms or Causes Cysts on fins, gills, and skin; labored breathing, excess skin mucus or pale skin. Suggested Action Treat entire aquarium with a commercial parasite remedy and improve water quality; freshwater dips can dislodge the parasites.


Ask a store partner about Petco's selection of books on cardinal fish and the variety of private brand products available for the care and happiness of your new pet. All private brand 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 or habitat contents to help prevent the potential spread of disease.

Pregnant women, children under the age of 5, senior citizens and people with weakened immune systems should contact their physician before purchasing 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.

This care sheet can cover the needs of other species.

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.

Developed with and approved by a qualified veterinarian.