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Asterina Starfish (Pros, Cons, & How To Get Rid Of)

Julien Renoult, CC BY 4.0, via Wikimedia Commons
Julien Renoult, CC BY 4.0, via Wikimedia Commons

Asterina Starfish (Pros, Cons, & How To Get Rid Of)

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Asterina Starfish is a marine invertebrate that prefers a coarse substrate such as stones, rocks, and sand. Due to this preference often makes its way into home aquariums by hitchhiking the live rocks that reefers buy from shops or other reefers.

Most people will define it as a pest or parasite, while others see it as a harmless and attractive addition to a reef aquarium. While some species of Asterina Starfish can live in harmony with corals, there are plenty of cases when they start preying on them due to the lack of other food.

This article will teach you everything you need to know about this starfish, including if you should keep it or not and how to remove it if that’s the case.

What eats asterina starfish?

The Harlequin shrimp is a known predator that only munches on starfish, and introducing this shrimp to your tank will help you get rid of Asterina starfish easily.

Bumblebee shrimp and Six Line wrasse can eat Asterina starfish as well, but it’s not their only source of food, and they might prefer to munch on something else more accessible.  

Asterina starfish identification

There are 15 known species in the world of this starfish. In general, the body shape of Asterina Starfish reminds you of a pentagon. The arms are short, and the tips are rounded. The legs are usually asymmetrical due to their method of reproduction (asexually by splitting in half).

The general color depends on the species, but it can be white, yellow, red, and grey. Sometimes reefers might see a blue Asterina starfish, but that is primarily a visual result of lights with a blue spectrum.

The size of Asterina Starfish is relatively small, being around 1/4” – 1/2” across and reaching a maximum size of 3/4” or 2 cm.

How to get rid of Asterina starfish

As we mentioned, the first tactic of removing this pest is by reducing the amount of food you add to the tank. This won’t help you remove them entirely, but it will help you stop their overgrowth. If you don’t reduce the amount of food inside the aquarium, they will reproduce faster than the removal rate.

Also, keep in mind that a massive die-off will produce a lot of ammonia as they rot, so you need to keep your water parameters in check and remove dead Asterinas.

Manual removal

Getting rid of Asterina starfish using some tools is one way to do it. Since they are too small to be grabbed by hand, some people remove them with tweezers. However, I find that extremely difficult, and you can easily injure it, which will only leave a leg or two behind, which will result in more starfish to deal with. If you have the skills and accuracy to do it this way, go ahead.

Turkey baster is another popular tool for sucking up Asterinas, and you can do it gently that it doesn’t harm them. You suck them up in the baster and get them out of the tank. This is my favorite way as well.

Manual removal can work but requires a lot of dedication. Depending on the level of infestation you have, you might need to do it for weeks to get it all out. And you need to hunt them at night or early in the morning when there is more Asterinas present.

Technological removal

Some reefers use high-tech equipment such as Lasers to remove pests from their tank, including the Asterina starfish. Lasers work at removing pests from the tank because they create a point of high temperature that burns the creatures you are pointing it at.

However, these lasers should be used with extreme care, only using protective glasses since they can cause blindness, and one should be very careful where to use them because they can refract on the glass and burn other inhabitants.

Biological removal

The most efficient and effortless way of removing Asterinas from your tank is to introduce natural predators inside the reef tank. The Harlequin shrimp is a known predator that only munches on starfish, and introducing this shrimp to your tank will help you get rid of Asterina starfish easily. The Harlequin shrimp is very popular in the reefing community for its ability to only eat starfish.

There aren’t many predators known to prey on Asterina starfish, but sometimes a Six Line Wrasse will eat them up. The efficiency of harlequins is given by the fact they prey exclusively on starfish.

If you have any decorative starfish in the tank, you should get it out if you introduce this predator because they will eat it too, no matter the size.

The shrimp’s ability to eat starfish is also a downside because once all the starfish are gone from the tank, the Harlequin shrimp will starve if you don’t give it other starfish to feed on.

After the job is done and the Harlequin does all the cleaning, you can give it to a friend that needs it or feed it with a Chocolate Chip starfish that you place in a sump. You can cut a leg off it each week and use it to feed the Harlequin shrimp. By next week the starfish will grow its legs back, and you can do it again. Therefore you can repeat the cycle without having to buy starfish anymore.

If you don’t have the heart to do this, you can return the Harlequin shrimp to the pet store, although constant aquarium switches can’t be suitable for any invertebrate.

Other Asterina starfish predators

There aren’t many reliable predators that you can use to get rid of Asterina starfish. Bumblebee shrimp and Six Line wrasse can eat Asterina starfish as well, but it’s not their only source of food, and they might prefer to munch on something else more accessible. Sea urchins are opportunistic omnivores and theoretically can eat a starfish, but they certainly won’t kill one. Therefore it is not a suitable predator either. That’s why Harlequin shrimp are the best Asterina starfish predator you can have since they only eat starfish. Considering you only have to think about what to do with them after they are done with the job, it’s a small price to pay to have such a hard-working invertebrate doing the pesky job of cleaning up the Asterinas from your tank.
harlequin shrimp
Image Credit: Live Aquaria

Asterina starfish - good or bad?

Most aquarists will say that Asterina starfish is not reef safe, firmly calling it a pest that needs removal. And there are good reasons to see them as such.

They are like weeds in your garden. They might be pretty at sight, but they can quickly get out of control and attack the precious livestock.

Some people have had this starfish in their tank for years without encountering any problems. In contrast, others have experienced the havoc it can bring if Asterina starfish gets a taste of corals. You should consider if it’s worth taking a chance and risk the life of your precious corals by keeping them around.

Some reefers like having Asterina starfish because they clean their tank from the overgrown algae on the glass and because some species are docile. However, you can never know what type of Asterina you have in your tank, and once they grow out of control, they will be hard to stop.

Do starfish clean tanks?

Yes, starfish are excellent cleanup crew members, munching on overgrown microalgae that spread all over the reef aquarium. 

What do Asterina starfish eat?

There are a few species of Asterina Starfish that are known to be “non-selective omnivorous.” That means they will eat anything they can find and grab on, including algae, corals, and polyps. Palm Tree Polyps, Corky Sea Fingers, and Zoas are the most frequent prey of Asterina Starfish.

The majority will also eat cyanobacteria, coralline algae, tiny worms, detritus, and diatoms.

Which Asterina Starfish eat coral?

The species of Asterina Starfish that will attack your corals are:

  • Asterina gibbosa – this starfish will eat everything inside your tank that can’t swim away, including corals and coralline algae.
  • Asterina stellifera – non-selective omnivorous feeders, sometimes even engaging in cannibalism if there is a high density of adults.

Should I remove Asterina starfish?

Considering some Asterinas can grow up to become coral predators, you should consider removing this starfish or keeping their number in check. If you start to notice damage on your coral’s polyps and there’s no other predator in the reef tank, then you should remove it from the tank immediately. As soon as it gets a taste from your corals, it only gets worse. There could be mistaken cases when another predator damages the coral. The starfish only does the cleaning, but that is only plausible when other predators are in the tank.

How do Asterina starfish reproduce?

Asterina stars have a fissiparous reproduction (fragmentation) where they split their bodies and lose one leg or two. Those legs will regrow as new starfish in the aquarium. That’s why Asterina starfish usually have an asymmetrical appearance, where each leg has different sizes. 

The way they reproduce can also make them outgrow the tank very fast if they have enough nutrition and no natural predator to keep them in check.

Asterina starfish care

Asterina starfish don’t need anything special to thrive in your aquarium. The only thing that you need to worry about is having a good supply of food available, so they don’t turn on your corals for nutrients.

Asterinas are very hardy and can survive even in low temperatures. As long as it is a source of nutrition in your reef tank, they can thrive on it. The number of Asterina starfish will be proportional to the bioload in the tank. That’s why one method of removing them is by reducing the amount of food you add to your tank.

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