One of the most common questions regarding saltwater aquariums is “What are those small starfish like things that I sometimes find on my corals?”
They are typically white and opaque in color, but their bodies can sometimes appear to be more translucent and may have a slight yellowish tint. People who are new to the hobby often confuse these stars for anemones, which is understandable since they usually share the same living environments.
They are referred to by many names such as Asterina Stars, Feather Stars, and Brittle Stars. Despite having such different names, they are all actually the same species of invertebrates, known as Asterina pectinifera.
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“Asterina is a genus of Asteroidea. Species in this genus occur in the Southern Ocean and Antarctica. Most species are found in the Ross Sea, but one is found in the Weddell Sea, two or three others are found south of Australia and one has been reported from the Siberian coast of the Arctic Ocean. ”
Asterina starfish are a common sight in reef aquariums, but many aquarists aren’t aware of their presence. The little grey star-shaped creatures are often mistaken for urchins, corallimorphs, or another type of coral. They are usually found on live rock and algae, and most often go unnoticed until they multiply to large numbers.
They are not standard aquarium fish. Many people will define this aquatic creature as a parasite or pest, while others see it as a harmless and attractive addition to any home tank.
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Asterina starfish are native to the waters around Australia.
Appearance and behavior
Asterina starfish can grow to a maximum size of three-quarters of an inch, but most are much smaller.
These are also called brittle stars or sea butterflies, are echinoderms related to sea urchins, sea cucumbers, and sand dollars.
They can be white, yellowish-grey, or brownish-grey and have five long, tapering arms with very short arms growing between them. Some Asterinas have all five arms while others have one or more missing. Some will have multiple arms of varying lengths.
The arms are surrounded by long spines that help them catch food, although they also feed on organisms attached to the substrate. They are capable of regenerating lost arms if they have enough food available and if they don’t get eaten first by other fish species who consider the Asterina tasty prey.
They can be hard to see because they tend to blend in with their surroundings and because they move slowly and deliberately. Their skin has many tiny spines which often make them feel rough to the touch.
Identifying the most common Asterias starfish in our tanks
The Asterina starfish belongs to the family Asterinidae and there are approximately 30 different species of Asterina starfish found in tropical waters around the world. There are three common species of Asterina starfish in the aquarium trade: Asterina miniata, Asterina pectinifera, and Asterina gibbosa.
Asterina starfish can be difficult to identify because they all look very similar when small. However, as they grow, there are several characteristics that can help you determine which species you have.
Asterina miniata
It is one of the most common Asterinas in the aquarium trade, where it is sometimes mistaken for the Brittle Star Ophiothrix fragilis. The main difference between these two is that Asterinas have five rays extending from each arm tip while Ophiothrix has only four rays per arm tip.
Asterina pectinifera
Asterina pectinifera emerges in the Sea of Japan, East China Sea and Yellow Sea as well as the southern part of Sakhalin and the eastern side of Russia’s Kamchatka Peninsula. It appears on rocky substrates at depths down to about 40 m (130 ft) and forms dense colonies. Each branch has a number of feathery feeding tentacles which are up to 70 mm (3.0 in) long.
The food of the Patiria pectinifera consists of diatoms and other microscopic algae. They are also known to eat zooplankton, for example copepods, amphipods and fish eggs. The starfish can consume up to 75% of macroalgae in the area it occupies.
Patiria pectinifera mainly eats filamentous algae, but it is also known to eat periphyton, which is a layer of algae that grows on submerged surfaces such as rocks and other hard surfaces.
Asterina gibbosa
Asterina gibbosa is a species of starfish in the family Asterinidae. It is sometimes known as the pentagonal starfish.
Gibbosa is a small, bright orange or red starfish that lives on sheltered rocky shores in the northeastern Atlantic Ocean and the Mediterranean Sea. The pentagonal starfish feeds on molluscs and other small creatures that get trapped between its five arms.
It is preyed upon by nudibranchs and fishes. Asterina gibbosa are dioecious; there are separate male and female individuals.
Asterina phylactica
Asterina phylactica is a small sea star with short blunt arms and a flattened shape. The surface has minute spines and there are rows of large spines at the tips of each arm, which give it its common name. So, these resemble spiny starfish too.
The underside has tube feet with suckers and tiny pincers for catching food. There is no madreporite (a raised plate through which water enters the water vascular system).
This species grows to a diameter of about 15 mm (0.6 in) and its colour may be olive-green, dark brown, or purplish-red, often with a central brown star-shaped marking on the upper surface. Its smaller size and its characteristic colouring make a difference with Asterina gibbosa to which it is related.
Asterina Starfish Diet
Just like serpent starfish, the Asterina Starfish diet is dependent on the temperature and availability of its natural food sources, but in captivity, it adapts to a limited diet if nutritional deficiencies exist. When this occurs, the Asterina Starfish may eat anything it can find and quite often will try to eat aquarium glass.
Some hobbyists have reported success in keeping the Asterina Starfish alive by feeding it shredded seafood (shrimp and fish) and live brine shrimp. Live phytoplankton, frozen or powdered marine fish foods are also acceptable for the Asterina Starfish.
As with most animals, the Asterina Starfish is capable of cannibalism. These can also catch prey with their tube feet if they are close enough. The tube feet are long and can extend beyond the edge of their body. They use these tube feet to apply suction when bringing food into the stomach.
It should be kept with tank mates that are no smaller than its mouth opening diameter. If a small piece of meat or fish happens to fall inside the tank or onto the substrate, it will be eaten immediately by the Asterina Starfish.
The diet of the Asterina starfish consists of the mussels and barnacles that cling to rocks and other surfaces in the intertidal zone. When the tide goes out, these small animals are exposed, providing easy prey for the starfish.
Asterina starfish can also consume detritus, which is essentially the dead remains of algae and other organisms that were consumed by higher-level consumers in the food chain.
Habitat
The habitat of the Asterina starfish is included in the shallow-water coastal regions, where there are ample amounts of coral reefs. It likes a temperature range from 45 to 55 degrees Fahrenheit. This can be seen in the Mediterranean Sea, the Aegean Sea, and the Caribbean Sea, where it is commonly found growing on hard or soft coral formations or other algae-covered surfaces.
Asterina starfish live on the bottom of the ocean floor where there is sufficient water circulation to allow them to move about freely. However, these animals do not live on sandy bottoms; rather they prefer rocky or coral reefs where there is an abundance of food for them to eat.
It is a solitary animal that spends its time foraging for food, eating, and reproducing. In the wild, it is not considered to be very aggressive, but when kept in captivity, it can sometimes become hostile toward other starfish.
Reproduction and Growth
This whole process can be divided into four stages:
1) Reproduction
2) Larval stage
3) Juvenile stage
4) Adult Stage
Asterina stars reproduce sexually and asexually. Both ways are similar to the reproduction of other sea stars.
In sexual reproduction, the female Asterina star releases eggs into the water, which are fertilized by male sperm and develop into free-swimming larvae that eventually settle on the seabed. Here they undergo metamorphosis into juvenile Asterina stars. The young use their tiny feet to attach themselves to a suitable surface, after which they lose their arms and develop into adult sea stars.
The asexual form of reproduction involves fragmentation of the body into numerous smaller individuals, each possessing a complete set of organs. This method of reproduction helps Asterina stars colonize new areas quickly, where there is less competition for food and space. The Asterina star can survive being eaten by its predators; this is because it reproduces by fragmentation, resulting in a great number of small offspring that are too small to be worth an animal’s effort.
How to recognize an Asterina infestation and what you can do about it?
The first sign of an Asterina infestation is tiny white spots on your corals or other sessile invertebrates. When these spots increase in number, they can look like a virus infection such as lymphocystis or coral pox. The difference is that the white spots on your coral won’t grow bigger and are mostly surrounded by healthy tissue.
Another sign of an Asterina infestation is the sudden disappearance (or heavy reduction) of microalgae from your aquarium glass or rocks. In nature, the Asterina starfish is part of a complex ecosystem containing a wide variety of algae-eating organisms.
This ensures that algae aren’t completely wiped out by any single species. In our closed aquarium systems, it’s very easy for a single organism to become dominant and wipe out all algae competition.
Are Asterina Starfish Suitable for Your Aquarium?
Asterina starfish are not usually recommended for a reef aquarium.
They are scavengers and will eat anything that is dead or dying in the tank. The asterina starfish’s main diet is algae, which grows on rocks, coral skeletons, and glass. While this type of feeding can keep your glass free of algae growth, it may also result in the starvation of fish.
Asterina starfish can be difficult to notice until they have grown large enough to be perceived as a threat to the fish population.
They feed on many types of reef aquarium fish including damselfish, clownfish, and even some butterfly fish. They have also been known to attack snails, sea urchins, brittle stars, and sea cucumbers. They are often introduced into an aquarium by live rock that has been collected from the ocean.
These starfish are often unnoticed by aquarists until they have grown to a considerable size and begun to consume fish in the aquarium.
Reasons To Have Asterina Starfish In An Aquarium
Asterina starfish eat algae so they can help keep your tank clean. Their feeding patterns also help stop your tank from becoming too dirty. They will eat algae as it grows and not after it has already been sitting in the aquarium for a while, which means less cleaning for you, their owner!
They are interesting and fun to watch. They move slowly but sure across the tank and this can be quite entertaining for both young and old fish owners alike.
They don’t require much care or maintenance once you get them set up in your aquarium. Of course, you still need to feed them and take care of them, but compared with other types of echinoderms, asterina starfish are very low-maintenance. Reasons Not To Have Asterina Starfish In An Aquarium
Reasons Not To Have Asterina Starfish In An Aquarium
Asterina starfish are very slow-moving, which means that they are not suitable for reef aquariums, where fast-moving shrimps and fish will out-compete them for food.
You might also notice that there are no Asterina starfish in public aquaria like London Zoo or Sea Life Centre .
They have a much thinner skin than other species of starfish which means that they can easily become torn or damaged if there are any sharp rocks or corals in your tank. Their soft bodies also make them much more vulnerable to predators such as damselfish and butterflyfish.
In addition, their relatively small size means that they have to eat more frequently in order to sustain themselves. If you are keeping a group of Asterina starfish you need to ensure that there is enough food available at all times otherwise they will start eating each other.
The Asterina starfish is not recommended for a reef aquarium because it tends to be quite sedentary compared with other species.
How to move a colony of Asterina starfish to another tank or aquarium system?
Sometimes you get Asterina starfish from another hobbyist, sometimes you get them as hitchhikers on live rock. And once in a great while, you might end up with an entire Asterina infestation!
The first step is to decide what you really want to do with the Asterina starfish. If it’s just a tough decision on whether to keep them or not, I’d recommend not keeping them.
Like most things in life, Asterina starfish are better served dead than alive. But if they are already in the tank and you want to move them somewhere else, here’s how to do it:
Step 1: Prepare your new aquarium
Before moving your Asterina starfish colony, prepare your new home. The ideal setup is a bare-bottom tank with no live rock or sand, but if you don’t have time for a full tank cycle, then place a thin layer of live rock on the bottom and add enough water to cover the rock.
Add activated carbon to help remove any medications you’ll use later. You may also want to add an ammonia remover like Amquel or Prime.
Step 2: Use stress coat
Next, prepare a mixture of saltwater that mimics the conditions in your display tank (but don’t match it exactly). Use stresscoat and other products like Stress Zyme to help minimize the effects of shock. This is a product that helps us avoid damaging the starfish when we start moving them around.
Step 3: Turn off lights
You don’t need these for this anyway and if they’re on it might make it harder to see your starfish. They also won’t like the light shining on them while you’re trying to move them (and they’re at their most vulnerable).
Step 4: Catch the starfish with a net
Use a net to scoop up your starfish, being careful not to hurt him/her. Put him/her into the new aquarium.
Want to Completely Remove from Your Aquarium?
- Put the Astrina Starfish in a bucket of fresh water, water from your tank is not recommended.
- Place your hand over the top of the bucket and shake vigorously for 3 minutes.
This will remove any excess slime coating and stinging cells (nematocysts) from the surface of the Astrina Starfish.
- After 3 minutes, pour out the water and refill with fresh water again into the bucket.
- Repeat step 3 with your hand over the top of the bucket again and shake vigorously for 3 minutes.
- Pour out water again, this time refilling with a mixture of 1 cup of chlorine bleach and 1 gallon of water.
- Place your hand over the top of the bucket and shake vigorously for 3 minutes.
The bleach solution will kill any remaining stinging cells (nematocysts) left on or in the Astrina Starfish. This process removes all stinging cells from its body and tube feet!