How to Care for Sea Urchins: Tank Setup, Feeding, & Compatibility Tips

Updated on March 24th, 2025

Scientific names: Lytechinus variegatus, Diadema sp., Eucidaris tribuloides, Tripneustes sp., Sphaerechinus sp., Echinometra lucunter, Mespilia globulus, Pseudoboletia maculata

With hundreds of species found in all five oceans, sea urchins can be found in a variety of water temperatures and depths. Although they do not have bones, urchins have a calcium carbonate skeleton with moveable spines that displays radial symmetry, meaning their body is made up of five equal parts.

An urchin’s mouth is comprised of five teeth, each with its own independently moving jaw which makes it easy for them to scrape food from surfaces such as rock or the walls of an aquarium. Like starfish, urchins have hundreds of tube feet that propel them along a surface and act as light-sensitive cells. They are nonaggressive and very slow moving, but always pay attention to where an urchin is residing in your tank to avoid accidentally being poked with their sharp spines.

Although most are not considered dangerous, urchins do contain a venom that can be painful; the flower urchin’s venom, however, contains a protein toxin called peditoxin. Marine inverts, such as urchins, are generally more sensitive and tolerate less environmental change than fish.

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This care sheet covers a variety of urchins, including:

Pincushion urchin
Black longspine urchin
Pencil urchin
Shortspine urchin
Rose pink urchin
Rock boring urchin
Tuxedo urchin
Hairy urchin

Typical appearance and behavior

Sea urchins come in a variety of sizes and colors; some species have long, thin spines, and others have short thick bumps or protrusions
Sea urchins have tiny claws on the surface of their shells in between their spines; these are thought to help urchins clean parasites and algae off their shells
Sea urchins have mouths with five teeth underneath their bodies; they feed using these teeth to grab and bite food and bore into rock
Sea urchins are primarily herbivores and spend most of their time grazing on algae and undersea vegetation, but they have also been known to feed on plankton, sponges, sea stars, mussels, sea cucumbers, carrion and polychaete (Bristle) worms.
Sea urchins are relatively easy to maintain as long as their tanks have stable temperature, specific gravity and pH
Because of their sharp teeth, urchins are not recommended for acrylic aquariums

Characteristics

Care difficulty	Beginner to advanced, depending on species
Average Life Span	Depends on species
Average adult size	Depends on species
Diet	Herbivorous
Minimum habitat size	10+ gallons, depending on species
Water temperature	72–78°F; urchins prefer cooler temperatures
Specific gravity	1.023–1.025

Habitat

Habitat size

A minimum of 10+ gallons is recommended for urchins; however, water conditions can change rapidly in smaller water volumes. A larger aquarium is recommended for larger urchin species.

Building your habitat

Water health -
- Provide proper filtration to ensure optimal water quality to help maintain health
- Provide slow to moderate water circulation, depending on species, to mimic water currents found in the urchin'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
Provide rocks and décor for hiding places
Live rock can provide a natural food source while also enhancing biological filtration

Feeding

Urchins will primarily consume algae; provide dried algae sheets, spinach or other greens if algae are lacking
Urchins will also consume leftover foods and decaying matter
Vitamins or trace minerals can be beneficial to all marine inverts

Things to remember when feeding your urchin:

Feeding depends on your aquarium’s condition; supplemental feeding should be offered if sufficient algae is not available

Urchin care

Water care: Maintaining great water quality with regular water changes and adequate filtration is important to help keep your urchin 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
Copper-based medications are toxic to marine inverts
Avoid overcrowded conditions, which are a major cause of stress and disease

Where to buy

In store and online. Urchins are available for purchase at Petco online and in store. If visiting your local location, please call ahead to check availability.

Supplies

Tank mates

Angelfish
Anthias
Basslets
Blennies
Butterflyfish
Clownfish
Damsels
Dartfish
Dragonets
Cardinals
Filefish
Foxface/rabbitfish
Gobies
Hawkfish
Lionfish
Pseudochromis
Reef-safe wrasse
Tangs

Introduce new inhabitants to the aquarium gradually.

Health

Signs of a healthy urchin

Bright, even coloring
All spines intact
Active feeding

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

Loss of color or appetite
Missing or deteriorating spines
Open sores or dissolving tissue

Common health issues

Little is known about diseases that affect invertebrates; as long as environmental conditions and food supplies are adequate, invertebrates are fairly resistant to disease.

FAQs

What do urchins eat? Urchins are primarily herbivores who feed on algae, but they are also opportunistic feeders and will consume leftover foods, detritus and carrion.
How do urchins eat? Urchins use their beak-like mouth, which is fitted with five sharp teeth, to scrape and consume algae.
How do urchins obtain oxygen? Most urchins do possess gills, but their gills do not provide most of their oxygen needs; instead, oxygen and gas exchange is done within their tube feet.
How does temperature affect urchins? Urchins live in a variety of water temperatures, but water that is too cold or too warm can cause issues with reproduction and even mortality.
How do urchins move? Urchins use their hundreds of tube feet to propel themselves.

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 cdc.gov/healthypets 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.