If you are looking to adorn your saltwater aquarium with some new and a somewhat unorthodox pet to care for, the Chocolate Chip Starfish (Protoreaster nodosus) might be your choice.
This starfish is a relatively big, colorful, and interesting sea creature. It is regarded as the Chocolate Chip Starfish because of the horned knobs on its upper side or arboreal surface, these make it look like a star-shaped cookie garnished with chocolate chips. This sea star is remarkable and its presence in the aquarium is nothing short of magnificent.
Keep reading for more information on this fascinating sea creature and how you can properly care for the Chocolate Chip Starfish in marine tanks.
Important: Chocolate Chip Starfish (Protoreaster nodosus) is currently subjected to threats such as large-scale harvesting and habitat loss. It is listed as endangered in Singapore.
Quick Notes about Chocolate Chip Starfish
|The Chocolate Chip Starfish
|Horned sea star, Horned Starfish, Chocolate sea star, Nodular Sea Star
|Tank size (minimum)
|20 gallons (~80 liters)
|Easy to medium
|24 – 27°C (~75°F – 79°F)
|SG = 1.021 – 1.025
|8.1 – 8.4
|8 – 12
|Less than 20 ppm
|Mostly Carnivore / Omnivore
|Non-aggressive fish only tank
|up to 17 years
|Typically, dark brown with shades of white, red, blue, yellow, or light tan
Origin and Taxonomy of Chocolate Chip Starfish
The Chocolate Chip Starfish is an amazing sea creature known by other names like Horned sea star and Chocolate sea star. It is a species of sea star seen in the warm, shallow waters of the Indo-Pacific regions. Mostly in the triangle formed by Seychelles, New Caledonia, and southern Japan.
The Chocolate Chip Starfish is one of the earliest animals named by Carl Linnaeus in 1758, and it is a member of the family Oreasteridae; a group of starfish which consists of robust species with short, thick arms.
Habitat of Chocolate Chip Starfish
Protoreaster nodosus, the Chocolate Chip Starfish can be found on sandy and muddy bottoms, seagrass beds in lagoons, and back reef areas where it feeds on benthic invertebrates.
This species dwells in shallow water, at depths of 1-30 meters (3 – 30 ft.), while the juveniles prefer shallow sandy habitats with abundant seagrass, they occur most at depths less than 2m (6 ft.).
This species of starfish is widely distributed across the tropical Indo-Pacific reef regions. It can be seen along the East Africa coastline and extends to the island of Madagascar, Indonesia, the Philippines, Southern Japan, and Australia.
Description of Chocolate Chip Starfish
Chocolate Chip Starfish possess rows of pointy/horn-shaped tubercles or knob-like protrusions on the upper surface of their star-shaped bod. These chocolate chip-esque knobs earned it the name “Chocolate Chip Starfish”.
Note: It is believed that these dark knobs also give them a fierce look, thus able to deter predators from harming them.
Chocolate Chip Starfish has a star-shaped calcified body with penta-radial symmetry, the outer body comprises of the central disk and stout arms.
The central disk can reach a diameter of 12 cm (5 inches) whereas the arms measure about 14 cm (5.5 inches). Additionally, the whole body of the starfish can attain a diameter of up to 40 cm (16 inches) although it is more common to see adult specimens between 20-25 cm (8-10 inches) in diameter.
The short and thick arms of the sea star are stunning. Most Chocolate Chip Starfish usually have five arms that extend towards the ends, sometimes they possess four or six arms but this is considered as an anomaly.
On the lower surface of their body, pale purple or transparent pink tube feet can be found, these are arranged in rows on each arm and extends to the endpoints.
The coloration of the Chocolate Chip Starfish appears in shades of white, yellow, brown or light tan, red, blue, and orange while the chocolate chips or knobs are variable in size, color, and pattern between specimens, they are typically dark brown.
According to the study, this starfish species is capable of living up to 17 years in the wild. Whereas in captivity, they usually live no more than 7 – 10 years if well-fed and the right water conditions are provided.
Behavior of Chocolate Chip Starfish
Chocolate Chip Starfish may be generally peaceful but that doesn’t stop them from preying on most sessile animals and these include corals and sponges in the tank as well as snails, sea urchins, bivalves and anemones.
Additionally, Chocolate Chip Starfish ingests food and ejects waste through the same opening – the mouth. They feed through eversion of their orange-colored stomach out of the mouth and onto their prey. As the prey is digested, the stomach gradually retracts into the mouth.
There is a small wart-like structure on the body of the starfish located on the side of the central disk, this is called the madreporite. This mechanism supplies the water canals that make up the water vascular system responsible for the movement of the mouth and the tube feet, the water vascular system also doubles as the starfish’s circulatory system.
The Chocolate Chip Starfish have the ability to close this madreporite to prevent air bubbles from getting trapped in the water vascular system.
Furthermore, the starfish will occasionally move about on the sand bed to eat biofilm, algae, and detritus. They host commensal animals like shrimp of the Periclimenes genus, tiny brittle stars, and juvenile filefish, these animals perceive the starfish to be a safe place and refuge to escape predators.
Lastly, if they are not freely roaming about on the substrate, you may see them affixed to the tank glass or live rock for a while, it’s pretty normal.
Feeding Chocolate Chip Starfish
They are scavengers, thus able to consume a huge variety of food found on the substrate bed. However, if there is a choice they prefer something meaty.
They also practice suspension-feeding, being able to capture and ingest food particles that are suspended in the water column and these include phytoplankton, zooplankton, detritus, algae films.
The Chocolate Chip Starfish will benefit from regular feeding of meaty foods such as shrimp, squid, bivalves, and lots more.
Instead of just throwing in meals hoping that they eat it, you may practice spot-feeding as it will help ensure that they get to the meal first before other inhabitants. You can equally pick the sea star up and place it on top of the meal.
How Often Should We Feed Chocolate Chip Starfish?
For the most part, they feed themselves. Mainly because they scavenge for food all the time.
However, if they have eaten all the algae in the tank, we can feed a bit of meaty food once every 1-2 weeks.
Is Chocolate Chip Starfish Coral Safe?
No, Chocolate Chip Starfish are not safe to keep in reef tanks. Moreover, they exhibit predatory behavior and will feed on corals, sponges, tubeworms, clams, etc. This is why they are ideal for FOWLR (fish-only-with-live-rock) systems.
Therefore, avoid keeping corals, sponges, anemones, and even smaller species of starfish because the Chocolate Chip Starfish will eat them.
Tank Requirements and Water Parameters
The recommended minimum tank size for housing a small Chocolate Chip Starfish is 20 gallons (80 liters). If you aim to keep larger specimens then you will need a bigger tank. The bigger the better.
Temperature: They will thrive best in optimal water temperature conditions, between 22 – 27 °C (72 – 81 °F).
pH: Maintain water pH value between 8.1 – 8.4
Water Hardness: The water hardness range should be between 8-12 dKH
Specific gravity: 1.021 – 1.025
Calcium: 380 – 430 ppm
The Chocolate Chip Starfish will do just fine in low-moderate lighting conditions.
Substrate and Decor:
It is best to house Chocolate Chip sea star in a tank with a deep sand bed about 4 – 5 inches (10 – 12 cm) in depth. Ideally, you need to provide plenty of live rocks and space them out properly on the sand bed.
Caring and Keeping Chocolate Chip Starfish
DO NOT introduce one to a tank that isn’t stable or hasn’t been running for quite some time.
Chocolate Chip Starfish are intolerant of sudden variations in water temperature and salinity levels. Also bad water quality due to high nitrate levels, ammonia, etc. can easily stress them. It may result in infections.
Exposing the starfish to air can be quite dangerous. The objective is to prevent air bubbles from making its way into the vascular system because it can paralyze and kill them.
If you want to transfer the starfish to a different tank for any reason, put them into a bucket or container filled with aquarium water and pour it into the new tank. Another method is to remove the starfish slowly, exposing the arms to the air first before the central disk so that the starfish can respond swiftly by closing the madreporite.
Important: Before you add new starfish to the tank, DO NOT forget to acclimate them so they can become acquainted with the new environment/parameters which are quite different from that which they experienced at the pet store.
Actually, this is the main reason why starfish often die after a week or two.
You can make them adjust to the new differences in salinity and temperature conditions by employing the drip method of acclimation. For example, 2 – 3 hours should be enough for the process.
Read more about drip acclimation here the principle is the same.
Additionally, never expose it to copper-based medications as this is lethal to their health.
Common Problems Associated with Chocolate Chip Starfish
Bacterial infections: The Chocolate Chip sea star is susceptible to bacterial infections which are often characterized by unusual spots and lesions.
Solution: These can be combated by treating with an iodine supplement or broad-spectrum antibiotic in a separate tank or container. They may equally sustain bruises and cuts from the live rocks. The good thing though is that they are capable of healing fast due to their regenerative ability.
Curled back arms: It is common to see some of the arms of the starfish curled back (an unusual position) while sitting on the glass, they do this to catch debris or algae film from the water column. This might be a sign of poor water quality.
Solution: Be sure to constantly check up on the starfish. If you notice it curling into a ball for long hours, that’s definitely not a good sign. Constantly test and monitor your water parameters to ensure that they are within the right ranges.
Reproduction of Chocolate Chip Starfish
They are able to reach sexual maturity at a diameter of about 8 cm (3 inches), usually when they are 2 – 3 years old.
Like most starfish species, the Chocolate Chip Starfish is dioecious, this implies having distinct male and female individual organisms. It is difficult to tell the gender of the starfish apart without dissection. Though the two genders occur in apparently similar numbers within each population.
In the wild, the sea star spawns in deeper water parts of their range. The spawning period is usually between March and May and it occurs at the full moon, this coincided with increasing water temperature and decreasing salinity.
The eggs of the Chocolate Chip Starfish are about 0.2 mm in diameter, these eggs metamorphose into larva that feed on planktons (tiny organisms), and will undergo several forms before developing into full five-armed sea creatures.
Breeding also occurs in the aquarium although it is not as common as it does in the wild, making it more difficult to achieve.
Chocolate Chip Starfish and Suitable Tankmates
Chocolate Chip Starfish can be paired with most small and peaceful fish species. For example, compatible fish tankmates are Tangs, Blue/yellow damselfish, Dwarf Angelfish, Clownfish, and Butterflyfish.
However, you should avoid keeping them with predatory fish like Triggerfish, Pufferfish, Parrotfish, Boxfish, etc.
Never keep the Chocolate Starfish and predatory shrimp such as Harlequin shrimp together. This shrimp species is carnivorous and eats only starfishes! Be careful with Coral banded shrimp, they are also pretty aggressive and strong enough to hurt the starfish.
Furthermore, this starfish species is not ideal for reef aquariums as it will feast on soft corals, sponges, anemones, and even smaller species of starfish.
Be careful with snails, the Chocolate Starfish can try to eat them, especially small ones.
Buying Chocolate Chip Starfish
This starfish species is readily available in fish stores, and getting one or two specimens for your aquarium won’t cost you a fortune because of its relatively low price (about 10 – 15 $).
You can easily obtain specimens that are about 10 cm (4 inches) in diameter in aquarium shops. At this size, these are likely to be about 5 or 6 years old.
Note: According to some studies, the corresponding growth rate is about 2 – 3 cm (0.8 – 1.2 inches) per year for small Chocolate Chip Starfish. However, once they reach 7 – 8 cm (3 inches), the growth rate slows down to 1 cm (0.4 inches) per year.
The Chocolate Chip Starfish is definitely a good choice if you are on the lookout for a unique and interesting sea creature to complement your saltwater tank.
To get the most out of your starfish and ensure that it lives for a long period. Feed it regularly to keep it well-nourished and fleshy, and maintain stable water parameters in the appropriate ranges.
However, before getting these cool alien creatures, you have to understand its requirements and the potential consequences. Impulse purchases often have a very bad effect on the reef tanks. People do not understand that their nature limits options if they want to keep them in a reef tank.
- Population dynamics, reproduction and growth of the Indo-PaciWc horned sea star, Protoreaster nodosus (Echinodermata; Asteroidea). Mar Biol (2008) 156:55–63 DOI 10.1007/s00227-008-1064-2.
- Recognition of individual knobby sea stars Protoreaster nodosus (L., 1758) using aboral surface characteristics. Journal of Experimental Marine Biology and Ecology 430–431 (2012) 48–55.