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Large Marine Fish Care Sheet

Developed with and approved by a qualified veterinarian.

This care sheet covers a variety of large marine fish, including:

  • Large angels
  • Tangs
  • Groupers
  • Large wrasse
  • Triggers
  • Tuskfish
  • Large lionfish
large marine fish


Angelfish are identified by the distinctive spine on their gill cover. Tangs are often called surgeonfish because of the scalpel-like spine at the base of their tail. Triggers have small mouths equipped with powerful jaws and teeth. Wrasses bring a wide variety of shapes, sizes and colors to most aquariums.

Table of Contents

Typical appearance and behavior

  • Large marine fish come in a variety of vibrant colors and patterns
  • Angelfish can be territorial; they tend to inhabit the middle and lower levels of the aquarium
  • Some tangs are solitary and territorial; they may be aggressive to new aquarium inhabitants
  • Some tangs, such as yellow tangs, may be kept in schools of three or more in odd numbers
  • Some triggerfish may be aggressive towards each other and other tank mates
  • Many wrasses like to bury themselves in the substrate at the bottom of the tank at night


Care difficulty Beginner to advanced, depending on species
Average Life Span Depends on species
Average adult size 6-24 inches long, depending on species
Diet Omnivorous, herbivorous or carnivorous, depending on species
Minimum habitat size 50+ gallons, depending on species
Water temperature 74–80°F, depending on species; some prefer temperatures outside these parameter
Specific gravity 1.020–1.025


Habitat size

Always provide the largest habitat possible for your large marine fish. A minimum of 50+ gallons is recommended for some species of juvenile large marine fish. As these species mature into adulthood, it is recommended to move them into larger aquariums for their health and wellbeing.

Building your habitat

  • Water health
    • Provide proper filtration to ensure optimal water quality to help maintain health; slow to strong water circulation, depending on species, should be provided to mimic water currents found in the large marine fish'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
    • A protein skimmer can help maintain great water quality and high dissolved oxygen levels
    • An aquatic heater should be used to stabilize water temperature, ensuring it does not fluctuate more than +/-2 degrees in a 24-hour period
    • The specific gravity should remain stable; do not allow specific gravity to fluctuate more than +/-0.001 in a 24-hour period
  • Décor - Provide rock and décor for hiding places and plenty of room for movement
  • Live rock can provide a natural food source while also enhancing biological filtration


A well-balanced large marine fish diet consists of:

  • Flakes, pellets, freeze-dried and frozen foods
  • Algae sheets should always be present for angelfish and tangs
  • Varied foods to ensure proper nutritional balance

Things to remember when feeding your large marine fish:

  • Feed 1–2 times daily, only what they can eat in 1–2 minutes; some species may need 2–3 feedings per day
  • Thaw frozen food before feeding

Large marine fish care

  • Maintaining great water quality with regular water changes and adequate filtration is important to help keep your large marine fish healthy
    • Daily: Check filter, water temperature, specific gravity and other equipment
    • Weekly: Check water quality at least once a week
    • Monthly: Change 10–25% of the total volume of water every 2–4 weeks, or as needed; change filter media monthly
  • Avoid overcrowded conditions, which are a major cause of stress and disease

Where to buy feather dusters

Large marine fish are available for purchase at Petco online and Pet Care Center; availability varies by location. If visiting you local Petco Pet Care Center location, please call ahead to check availability.


Tank mates

  • Compatibility will vary by species
  • Many large marine fish species are compatible with other large marine species; always check a compatibility chart
  • Several large marine fish species are territorial and will fight with their own species, unless a mated pair
  • Introduce new inhabitants to the aquarium gradually


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 veterinarian)

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

Common health issues

Health Issue Symptoms or Causes Suggested Action
Fin rot Frayed or disintegrating fins; the base of the fins usually reddens Improve water quality; consult your local aquatic specialist or aquatic veterinarian for treatment
Marine ich or marine velvet Cysts on fins, gills, and skin; labored breathing, excess skin mucus or pale skin Quarantine fish immediately and use a commercial parasite remedy; complete a water change; freshwater dips can dislodge the parasites; consult your local aquatic specialist or aquatic veterinarian for treatment
Bacterial infections Cloudy eyes, open sores and/or reddening of the skin Improve water quality; use a commercial antibacterial remedy as directed; consult your local aquatic specialist or aquatic veterinarian for treatment
Viral infection (lymphocystis) White nodule growths on fins or body Improve water quality; consult your local aquatic specialist or aquatic veterinarian for treatment

Additonal 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 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 the Centers for Disease Control at for more information about aquatic life and disease.

The information on this care sheet is not a substitute for veterinary care. If you need additional information, please contact your veterinarian as appropriate.