Starfish Care Sheet

What Is a Starfish?

Starfish are a large family of marine invertebrates that use their star-shaped bodies to sift through sand and debris.

This care sheet outlines the basic care needs for different types of starfish species, including: 

• Chocolate chip starfish

• Sand-sifting starfish

• Red knob starfish

• Red Luzon starfish

• Blunt spined brittle starfish

• Red Linckia starfish

• Green brittle starfish

• Red marble starfish

Despite their common name, starfish are not fish. 

Since they don’t have blood or a heart, starfish use a vascular system that circulates vital nutrients and saltwater through their body.  

Like other marine invertebrates, starfish are highly sensitive to changes in their environment and do not tolerate them well. Because of this, it’s important to provide them with stable water quality, salt concentration, and water temperature. 

Starfish Anatomy 

Most species of starfish have five arms, which gives them their characteristic appearance. Starfish can be found in a variety of vivid colors, including yellow, red, and purple.  

Starfish can regenerate detached limbs. This process also enables some species to grow new starfish by breaking off a limb. 

Aside from sand-sifting and brittle starfish, which lack a suction cup on their tube feet, starfish have a system of tubular feet on the underside of their body and a foot-like suction cup that they use to anchor themselves to a surface. 

To eat, starfish eject their stomach through their mouth, surround their prey with their stomach, and digest the food outside of their body. A starfish’s mouth is located at the center of their body, on the underside where all of their arms meet.

Starfish are slow-moving invertebrates that spend most of their day searching for food.  

Starfish Characteristics 

Starfish Supply Checklist

To keep a starfish happy and healthy, aquarists should have these basic supplies on hand: 

• Appropriate-sized aquarium 

• Appropriate food, dry and frozen 

• Decor 

• Marine aquarium salt 

• Marine substrate 

• Water conditioner 

• Filter 

• Water test kit 

• Full-spectrum lighting 

• Net 

• Protein skimmer 

• Thermometer 

• Heater 

• Refractometer 

• Live plants 

• Aquarium hood/cover 

• Live rock 

Starfish Habitat

Depending on the species, small starfish will need a minimum tank size of 10 gallons. Larger species will need a much bigger habitat to move and explore comfortably. 

Starfish aquarists should always provide the largest habitat possible, especially because smaller aquariums are more sensitive to changes in water conditions than bigger ones. 

Starfish Tank Mates 

Starfish can be housed in a community tank alongside a variety of peaceful fish, including: 

• Dwarf and large angelfish 

• Anthias 

• Basslets 

• Blennies 

• Butterflyfish 

• Cardinals 

• Clownfish

• Damsels 

• Dartfish 

• Dragonets 

• Filefish 

• Foxface rabbitfish 

• Gobies 

• Hawkfish 

• Pseudochromis 

• Reef-safe wrasses 

• Tangs 

Do not house starfish in the same aquarium as boxfish, puffer fish, or triggerfish. These species are predatory and will try to eat starfish. Starfish should not be kept in overcrowded aquariums, as these conditions often lead to stress and disease in the tank.

New tankmates must be introduced to an aquarium gradually, and aquarists should remember that their tank’s ammonia, pH, and nitrate levels will change when a new fish is introduced. These parameters need to be monitored carefully after adding new fish.   

Filtration 

A filter system is an essential addition to any aquatic habitat. Aside from keeping tanks looking clean, filters remove harmful toxins like ammonia from the aquarium’s water and add oxygen to the water. 

Look for a filter with an adjustable flow rate that can create slow to moderate currents in your starfish’s tank. Power filters (also known as “hang-on-back" filters) and external canister filters are recommended because they offer effective mechanical, biological, and chemical filtration and do not take up any space inside an aquarium. 

Tip: The aquarium’s filter should be powerful enough to process all the water in the tank at least four times an hour. For example, a 30-gallon tank should ideally have an aquarium filter with a flow rate that’s at least 120 gallons per hour (GPH).

Starfish Water Health and Salt Content  

Like other marine invertebrates, starfish are more sensitive to changes in water quality than fish. Ideally, starfish should only be added to a well-established tank that already has stable and balanced water conditions. 

Regularly test your aquarium’s water to ensure its pH, ammonia, nitrate, and nitrite levels are stable and within a safe range. An aquarium test kit can be used to measure key water parameters quickly and accurately. Additionally, a protein skimmer can be used to help maintain the tank’s water quality. 

As saltwater species, starfish require salt in their aquarium to survive. When setting up their tank, gradually add small amounts of marine salt to the water until its specific gravity reaches between 1.023 and 1.025.

The specific gravity reading should not fluctuate by more than +/- 0.001 within a 24-hour period. This helps let you know that the salt amount in the water is appropriate. Too much fluctuation can be detrimental to the health of your starfish. Use a hydrometer or refractometer (salt level tester) to measure the salt concentration and specific gravity of the aquarium’s water. 

Temperature 

Starfish thrive in water temperatures from 72 to 82 F. The water’s temperature should not fluctuate more than +/- 2 degrees within a 24-hour period.  

Install an aquatic heater with a built-in thermostat in your aquarium to keep the water temperature within the ideal range. Use an aquarium thermometer to check the tank’s water temperature daily. 

When selecting a heater for the tank, keep a few things in mind: 

• Some modern heaters have a built-in thermostat, while others need to be paired with a thermostat that’s purchased separately. 

• As a general guideline, aquarium heaters need between 2.5 and 5 watts of power for every gallon of water in the tank. For example, a 10-gallon tank requires a 25- to 50-watt heater. 

Larger aquariums with a volume over 50 gallons may require two smaller heaters placed on opposite sides of the tank to prevent cold spots from developing in the water. 

Starfish Tank Accessories

Note that, like all pets, starfish need plenty of stimulation to stay happy and healthy! The bottom of a starfish’s tank should have a variety of surfaces—including sand, rocks, and coral—to keep the starfish entertained.  

Substrate

The bottom of a starfish’s tank should be lined with at least 1–2 inches of substrate. Certain species, such as the sand-sifting starfish, require a deeper layer of soft, sandy substrate that they can search through to find food. 

Aquariums need about 1.5 pounds of substrate for each gallon of water in the tank. For example, a 10-gallon tank will require about 15 pounds of substrate to create a 1- to 2-inch layer. 

Be sure to rinse the substrate with clean, running water before adding it to the tank.  

Hiding Places and Decor

When not searching for food, starfish spend most of their day hiding in rocks and crevices. Therefore, a starfish’s tank should include plenty of rock, coral, and other hiding places. 

Avoid using decor made of copper, as it can be fatal to starfish. 

Make sure that rocks are spaced out and do not clutter the tank, as starfish need plenty of open space to move around! 

Starfish do not require plants in their tank and may uproot them while searching for food. If you choose to add live plants, select those with sturdy roots, such as java fern and anubias.  

Live Rock

In addition to serving as a food source and hiding place, live rock enhances biological filtration in a starfish’s tank. 

Live rock is not actually alive! The term “live” refers to the beneficial bacteria and macroscopic life that live inside and on the surface of the rock, not the rock itself.  

Before adding live rock to the tank, it should be tested and treated to remove dead or decaying microorganisms, as these can increase ammonia levels in the tank.

Pet parent aquarists should always wear gloves while handling live rock or performing any maintenance on their aquarium. 

Protein Skimmer

Adding an appropriately sized protein skimmer to a starfish’s aquarium can improve water quality and increase dissolved oxygen levels in the tank.  

Starfish Tank Cleaning

Maintain your starfish’s tank by performing routine water changes of no more than 10–25% of the total water volume every two to four weeks. Newly added water should be at the same temperature and have the same salinity (salt concentration) as the existing water in the tank. 

Avoid draining and replacing the aquarium’s entire water volume, as this will remove the beneficial bacteria essential for keeping the habitat’s ecosystem healthy.  

Most aquariums will need a full cleaning once a month, depending on the number of fish and invertebrates in the tank.

What Do Starfish Eat?

As carnivores, most pet starfish primarily feed on commercially available fresh, frozen, freeze-dried, and pelleted meaty foods. Some omnivorous species will also eat algae and bacteria, while others also feed on corals. Like all marine invertebrates, starfish benefit from a diet high in calcium and other vitamins and trace minerals. 

Feed starfish two to three times a week, depending on the species. Frozen foods should be thawed before feeding. 

Starfish Care

Anti-parasitic and copper-based medications are fatally toxic to starfish and should never be used in their tank. 

After a new fish, invertebrate, or piece of equipment is added to the aquarium, it’s important to test the tank water’s quality weekly for at least two months to ensure that pH, nitrite, ammonia, nitrate, carbonate, and general hardness levels remain within the ideal range.  

If the test results are consistently safe after two months, you can reduce testing to once a month. 

Water test kits have an expiration date and should be replaced yearly.  

Monitor your aquarium’s water level and top it off as needed. Before adding new water to an aquarium, treat it with a water conditioner to remove toxic chemicals like chlorine, chloramines, and heavy metals.  

An aquarium’s filter, water temperature, and other equipment should be checked daily to ensure they’re working properly. Filter media should be replaced monthly or rinsed in old tank water during water changes, depending on water conditions and the number of fish and invertebrates in the tank. 

Follow the use, care, and maintenance instructions provided by the manufacturer of your filter system.  

Do not use hot water, bleach, or chemicals while rinsing filter media, as this will kill the beneficial bacteria that help keep the aquatic environment safe, clean, and stable.  

Avoid replacing all the filtration media in the aquarium at the same time, as this can also remove beneficial bacteria from the tank.

Starfish Veterinary Care

Annual Care

Annual or biannual examinations with a certified aquatic veterinarian are strongly recommended.  Some aquatic veterinarians will even perform telehealth video consultations.

Your starfish and setup should also be assessed by a veterinarian within a week or two of establishing them in your home. While you can transport your starfish to a vet, it is recommended that you find an aquatic veterinarian who can make a house call to avoid transportation stress.

Signs of a Healthy Pet

• Bright, even coloring

• All arms are intact

• When feeding, the starfish is active

When to Call a Vet

• Changes or loss of color

• Decreased or no appetite

• Sores or ulceration

Common Illnesses in Starfish

• Sea star wasting disease

• Injury or loss of arms

• Parasitic, bacterial, fungal infection

• Anorexia (not eating)