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Marine Invert

includes starfish, feather dusters and urchins

The unique appearance and bright coloring of starfish provide an appealing addition to aquariums. Feather dusters are a type of fan worm found in coral rubble in most tropical waters around the world. Sea urchins have a calcium carbonate skeleton with moveable spines. Marine inverts are generally more sensitive and tolerate less environmental change than fish.

Marine Invert

Marine Invert Facts

Average Adult Size depends on species
Average Life Span depends on species
Diet omnivore and carnivore
Minimum Aquarium Size 29+ gallons, depending on species
Water Temperature: 72-78°F
Salinity Level: 1.023-1.025


A well-balanced marine invert diet consists of:

  • Feather dusters eat live floating micro-plankton.
  • Many starfish are carnivores and feed primarily on commercial frozen food (meat source); small starfish can eat micro-algae.
  • Urchins will consume detritus (decayed matter) in tank but prefer algae; Provide dried algae sheets, spinach or other greens if algae is lacking.
  • Vitamins or trace minerals can be beneficial to all marine inverts.


Things to remember when feeding your marine invert:

  • Feather duster - Feed supplements 2 to 3 times per week by dispersing food just upstream with a pipette or straw.
  • Starfish - Feed 2 to 3 times per week, depending on species.
  • Urchins - Feeding depends on conditions of tank; do poorly in tanks unless supplied with an ample amount of algae and greens.
  • Thaw frozen food before feeding.


  • Keep in an appropriately sized aquarium; full spectrum lighting and proper filtration are essential.
  • The use of copper-based medications is toxic to marine inverts.
  • 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

  • Feather dusters are peaceful filter feeders that can be kept singly or with other annelids.
  • Starfish typically have five arms extending from a central circular body; can regenerate limbs.
  • Urchins use their tube feet to move across the bottom of the tank while they scrape algae with the sharp teeth on their underside. Not recommended for acrylic aquariums.

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 to 4 weeks, or as needed.
  • Introduce new inhabitants to the aquarium gradually.


  • Check the Petco marine compatibility chart for more information for your marine invert species.


Signs of a Healthy Marine Invert

  • Bright, even coloring
  • Urchin has all spines intact
  • All starfish arms are intact
  • Extended tentacles on feather duster and tube are intact
  • Avoid overcrowded conditions, which 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
  • Limp plume of tentacles
  • Missing or deteriorating arms
  • Open sores or dissolving tissue

Common Health Issues

Health Issue Symptoms or Causes Suggested Action
Health Issue Little is known about diseases that affect invertebrates; as long as environmental conditions and food supplies are adequate, invertebrates are fairly resistant to disease. Symptoms or Causes   Suggested Action  


Ask a store partner about Petco's selection of books on marine crustaceans 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 the Centers for Disease Control at 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.