How To Remove Asterina Starfish From Your Tank

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If you have a reef tank, then you may have come across an asterina starfish at some point. These small creatures can be a nuisance in a reef tank, as they can multiply quickly and consume corals and other invertebrates. In this blog post, I will discuss how to remove asterina starfish from your tank safely and effectively. Let’s start with the first question.

What Are Asterina Starfish?

Asterina starfish is the common description and parent genus for about 15 different species of marine starfish. These starfish, also less commonly known as bat stars, can be found in many ecosystems throughout the world, including the Atlantic, Indian, and Pacific Oceans.

In fact, species of asterina have been found around coral reefs with temperatures below 50° F and at varying depths. Most of these starfish can be found in shallower reef conditions though they have been observed at depths as deep as 150 meters1.

In the reef aquarium, all species of Asterina are categorized as asterina regardless of their true classification. There are usually too many superficial similarities between these species to differentiate between the exact type.

In general, these starfish are less than a half-inch wide and have an asymmetrical appearance with missing and uneven legs, which is much different than the typical 5-point radial symmetry displayed by echinoderms.

Most asterina starfish are similar in appearance otherwise. They are largely white or tan in coloration but may have brown or red shading or markings. However, it seems that coloration gives some insight into the behavior of the starfish; some species have been known to be more destructive than others which can make it difficult for hobbyists to decide whether or not to keep this pest in their reef tanks.

The problem with asterina starfish is that they are naturally good members of the cleanup crew despite their appetite for corals. At the same time, hobbyists have had many problems with them destroying coral colonies and overpopulating the tank in a matter of weeks.

How Did Asterina Starfish Get In Your Aquarium?

Asterina starfish are a common saltwater hitchhiker. This means that they are introduced into the aquarium by way of something added to the tank, like live rock, coral frags, or used substrate.

As adults, asterina starfish are small and difficult to spot on their own. Add in the fact that they are able to regenerate from a very small piece of flesh and it can be very easy to miss an incoming asterina starfish infestation.

How Do Asterina Starfish Reproduce?

Like many echinoderms, asterina starfish reproduce through fissiparous reproduction. This process allows them to detach a given leg, which then grows into an entirely new starfish. As you can probably guess, this can quickly lead to an asterina infestation within the aquarium.

In addition to fissiparous reproduction, some species of asterina are also hermaphroditic. They also have the ability to sexually reproduce through egg production.

Are Asterina Starfish Good Or Bad?

There is a lot of debate about asterina starfish in the saltwater aquarium hobby. No matter who you ask, these sea stars are known as pests regardless of the benefits they can bring to the marine ecosystem. This is largely due to their rapid reproduction rates, which can be unappealing to some hobbyists even though there are many benefits to having a sustainable asterina population.

There is no clear answer as to if asterina starfish are good or bad. Most aquarists welcome them into their reef aquariums as active members of the cleanup crew, but can quickly learn to hate them if there are any signs of damage to corals.

It has always been a question about whether or not these starfish clean up after already dying corals, or if they take the first step towards eating them due to their natural diet.

It is largely believed that darker colored starfish and ones with red or brown markings are much more likely to eat corals than those that are almost entirely white, regardless of if decay has set in or not. Hobbyists have gone as far as holding controlled experiments to test this hypothesis, which resulted in some definite findings.

One experiment, in particular, demonstrated asterina starfish actively crawling over and grazing on a colony of zoanthids. At the same time, they have been seen eating coralline algae, other stubborn algae species, and even cyanobacteria.

Should You Remove Asterina Starfish From Your Aquarium?

Again, there is no right answer to this question until it’s too late.

The truth is that asterina starfish are likely to make their way into your tank if you’re keeping corals. It can take considerable time and effort to remove every asterina star you see afterward, but removal may be the best option if you have a reef tank filled with expensive zoanthids and soft corals.

As mentioned before, it’s largely believed that the color and species of asterina starfish play into the likelihood of corals being eaten. If you find that you have a dark-colored variety of starfish, then it’s probably better to be safe than sorry. However, if your stars generally lack markings and have light coloring, then they can be a great addition to the cleanup crew by eating algae and detritus while keeping coralline algae in check.

How To Remove Asterina Starfish From Your Aquarium

If you don’t want to take the risk of asterina stars eating your coral, then you’ll need to know how to remove them. The best way to prevent asterina species from entering your system is by catching them before they have the chance to get comfortable. Luckily, there are a few other ways, including several livestock options, that you can deal with an asterina starfish infestation.

Prevention

The best way to stop any pest from taking over your saltwater reef aquarium is by stopping the problem before it happens.

There are a few ways that asterina stars might enter your system. The most common ways are through the introduction of live rock, coral frags, or used filter media. If you’re sourcing materials from a fellow hobbyist, then it is worth knowing if they have asterina starfish in their aquarium. This can help you be better prepared before accidentally transferring a new pest into your system.

Regardless, live rock and coral frags can be observed for asterina species through a quarantine process. Corals frags can even be dipped into a coral dip, like Coral RX Pro Dip or Bayer BioAdvanced Insect Killer, for extra precaution. Keep in mind that these solutions may not affect asterina starfish eggs and may leave some adults as well.

Coral RX Dip

Coral RX dip is the standard for coral dips in the aquarium industry. There are others out there, but this is the original and most used.

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Steps can be taken to stop these pests from entering your tank. If one happens to get past this process, remember that they have the ability to reproduce asexually at very fast rates; one asterina star can turn into a whole population in a matter of days.

Reduce nutrients and wastes

Asterina starfish are scavengers and opportunistic feeders. They graze on algae, biofilm, and their favorite corals, zoanthids.

As a pest, these invertebrates rely on what is already present in the aquarium to thrive. This means that population growth directly correlates to the resources readily available in the reef tank; a large amount of algae will result in a large number of asterinas.

Though reducing nutrients and wastes isn’t the best option if your aquarium is relatively stable otherwise, it’s a possible solution for at least slowing the growth of the asterina population.

Manual Removal

If you already have asterina starfish in your aquarium, then your tank will probably never be rid of them. However, you can greatly reduce population numbers through regular manual removal.

Manual removal is simple, though additional maintenance. The best tactic is to wait until the lights go out on the reef tank and then remove every tiny starfish you see. These sea stars can be humanely euthanized with a coral dip or other solution.

Never try to kill these starfish while they’re still in the aquarium! Any fragments leftover from a dead asterina starfish still has the possibility of recovering into a new starfish.

Otherwise, simply remove them as you find them. Some hobbyists like to transfer them from the main display to the sump, though they can always find their way back up to the aquarium.

What Eats Asterina Starfish?

Luckily, there are a few species that will eat asterina starfish.

It’s important to remember that adding livestock to solve a pest problem is not a temporary solution; your new addition should feel comfortable in its new home long after the pests are gone!

As we’ll see, some of these livestock can be challenging to keep due to their dependence on asterina starfish as their main food source. For some hobbyists, these challenges definitely outweigh the risk of having their soft corals eaten though.

Harlequin Shrimp (Hymenocera elegans)

  • Scientific name: Hymenocera elegans
  • Maximum size: 2 inches
  • Minimum tank size: 10 gallons
  • Origin: Indo-Pacific
  • Reef-safe: Yes

Harlequin shrimp are the most recommended natural solution for an asterina starfish infestation. These small shrimp have very appealing patterning with pastel blue, pink, and purple spots on top of a creamy base color. They also don’t require much space as long as dietary needs are met. It is the preferred method of many reefers, including longtime YouTube influencer Rotter Tube Reef – who’s video is showed above.

The unique thing about the harlequin shrimp is that they’re one of the few species of shrimp that is truly reef-safe. Instead of algae and other organics, their diet consists of only echinoderms, like asterina starfish. In a matter of weeks, harlequin shrimp will eradicate an asterina problem. After that, a bigger problem arises.

Once all asterina stars have been eaten, your shrimp will be left without any food. At this point, hobbyists need to start supplementing feedings or rehome the shrimp to another hobbyist with an asterina problem.

If you want to keep your harlequin shrimp, then there are a few options for keeping them fed. One of these options is to set up a system solely dedicated to raising asterina starfish. This system does not need to be complex and can be similar to a refugium setting.

Another option is to regularly buy echinoderms, like chocolate chip starfish (Protoreaster nodosus) and Linckia sp. (orange linckia, red linckia, and blue linckia). Chocolate chip stars are much more available and hardier than Linckia sp., making them the better option for easier feedings and long-term success.

These starfish can be fed all at once or by one leg at a time, though the latter isn’t for the faint of heart; the only advantage to feeding leg by leg is that the starfish will have time to rejuvenate a new one by the next feeding, reducing future costs.

Harlequin shrimp are expert hunters. They will work together to flip a starfish on its back and start to eat its tube feet. They will slowly but surely work their way towards the fleshy center of the starfish.

Luckily, it can take up to a month for a harlequin shrimp to eat an entire starfish before having to buy another.

Bumblebee Shrimp (Gnathophyllum americanum)

Bumblebee Shrimp
  • Scientific name: Gnathophyllum americanum
  • Maximum size: 1 inch
  • Minimum tank size: 10 gallons
  • Origin: Indo-Pacific
  • Reef-safe: Yes

The bumblebee shrimp, also known as the striped harlequin shrimp, is one of the most affordable options for long-term asterina control, but also one of the hardest to maintain due to water parameters.

These shrimp are named after their alternating black, white, and yellow stripes that line their body. Bumblebee shrimp are very similar to harlequin shrimp in diet and behavior but are more accepting of other foods outside of echinoderms.

Bumblebee shrimp will actively hunt and eat asterina starfish in the tank. However, bumblebees will also eat algae, waste, and any leftover food they happen to come across. This is beneficial for hobbyists that plan on keeping their shrimps after all asterinas have been dealt with but might interfere with the efficacy of eliminating the pests.

If deciding between a harlequin and bumblebee shrimp, consider how immediate your problem is. Harlequin shrimp will eliminate all starfish within a couple of weeks while bumblebees might take a little longer and might be better at population control rather than total eradication.

After the asterinas are gone, also consider how you will continue to feed your shrimp. Bumblebees are easier in the long run, though harlequins are much faster at solving the immediate problem.

Bongo Shrimp (Phyllognathia ceratophthalma)

Tiger Shrimp
  • Scientific name: Phyllognathia ceratophthalma
  • Maximum size: 1 inch
  • Minimum tank size: 10 gallons
  • Origin: Indo-Pacific
  • Reef-safe: Yes

The bongo shrimp is rarely seen in the aquarium hobby but has become a popular solution for asterina starfish infestations. Though these shrimp might be harder to find than harlequins, they’re usually cheaper and much more suited for smaller home aquariums.

Bongo shrimp are small shrimp that rely only on echinoderms for food. They have a white body covered in bright orange and blue markings.

Bongo shrimp are extremely shy and do not do well in tanks with large, active fish. Because of this, hobbyists usually keep them in nano and pico tanks with docile fish that have no interest in eating them; even then, these shrimp are likely to hide in the shadows of the rockwork.

It is believed that bongo shrimp favor brittle starfish (Ophiuroidea class) more than asterina starfish, but they will still greatly help to reduce populations.

Final Thoughts

Asterina starfish are a common pest in the aquarium world that you’re likely to find in your own reef tank one day. For the most part, these tiny starfish are nothing to worry about. However, some species of asterina starfish can begin to munch on zoanthids and other soft corals without any notice. Their ability to quickly reproduce can also cause an infestation in no time.

Luckily, there are a few ways to control and even completely eliminate all threats of an asterina starfish infestation through prevention, nutrient and waste reduction, and manual removal as well as several natural coral predators.

by Mark

Mark is the founder of Aquarium Store Depot. He started in the aquarium hobby at the age of 11 and along the way worked at local fish stores. He has kept freshwater tanks, ponds, and reef tanks for over 25 years. His site was created to share his knowledge and unique teaching style on a larger scale. He has worked on making aquarium and pond keeping approachable. Mark has been featured in two books about aquarium keeping - both best sellers on Amazon. Each year, he continues to help his readers and clients with knowledge, professional builds, and troubleshooting.

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