What Do Starfish Eat? Complete Food & Diet Information

Everyone knows what a starfish is, but very few understand its structure and functioning. They are very unique and interesting aquatic creatures!

This is especially true for anyone planning to keep one in their home aquarium. For many potential starfish owners, the process of feeding them can seem quite daunting (or confusing).

This guide will explain what starfish eat, how their diet varies by location and species, and how they actually consume their food.

How do starfish eat?

Right off the bat, the very act of eating a starfish may seem quite strange. These iconic creatures barely seem to move and don’t appear to display “normal” feeding behavior.

So how do they do it?

To understand this, we need to delve into their anatomy. Specifically, we need to understand their feet, arms, and bellies (yes, they have two bellies).

At the bottom of each of their arms, a starfish has thousands of little feet. These look like short tubes and this is how these creatures move slowly over various surfaces in the water.

A starfish after eating

But there is more. A starfish also has an eye under the end of each of its arms. This helps them navigate and search for food to eat.

Now let’s look at their stomach situation. Starfish don’t just use their stomachs for digestion, they actually use it to “seize” the food they want to eat.

Here’s how the process works:

First, a starfish will move until it is above what it wants to eat. As you can imagine, it’s not a quick process (and their vision isn’t stellar). This is why these sea creatures are basically looking for food all the time.

Once the starfish is in position, things get pretty interesting. Through a process called eversion, the starfish will actually push one of its stomachs (the heart stomach) out of its mouth and envelop the food it is about to eat. They are quite skilled with this action and can even slip their heart stomachs into tiny mollusk shells. This process allows the starfish to begin digesting and absorbing its food with stomach acid.

Once this process is complete, they will “retract” their heart stomach and pass the rest of the digestion process to the pyloric stomach (i.e. stomach number two).

The advantage of this process

You might be wondering why starfish would eat this way. It seems like there are a lot of unnecessary steps, right?

But as always, nature has a reason.

By bringing its stomach outside its body to break down and digest food, a starfish is able to eat food that would normally be too large for it. Instead of needing the extra room to swallow a large snail, oyster, or clam, they can essentially “liquefy” the important stuff to aid digestion.

This makes these animals one of the most efficient eaters in the world!

What do starfish eat in the ocean?

Starfish have a varied diet in the wild. This is influenced by their location and nearby food or prey.

From a wide vantage point, you’ll often see starfish happily eating mussels, oysters, clams, and snails. They are the perfect prey as they can be easily digested using the method described in the section above and are easy to catch. But that being said, some will even eat fish (if they are able to pick one up).

A chocolate chip starfish that eats various large molluscs

In other situations, some starfish will eat sea urchins, barnacles, silkworms, coral polyps, and crabs. There is a lot of variety in their diet, and it all depends on where the starfish lives and what food is available to it.

Author’s note: Crabs are usually only on the menu for large starfish. On the other hand, coral polyps are an important part of the diet of starfish (like the crown of thorns) that live in large reef systems. . Some starfish will even eat other starfish! Like any food ecosystem, availability plays a big role.

Because starfish are constantly moving in search of food, they will also do a bit of scavenging. This is especially true for starfish which are not very large. Foods like algae, algae, and decaying animals or plants will be taken care of quickly (making them useful for some home aquariums).

What do starfish eat in aquariums?

To provide the right food for your starfish, you need to understand the species you have and their natural environment. This usually means you’ll need to provide some variety if you want these creatures to thrive (you can’t go to the store and just buy “starfish food”).

That being said, they will generally consume foods that occur naturally in your aquarium. For more home aquariums, this usually means algae that has accumulated on various surfaces as well as fish food that has been missed by other aquarium inhabitants.

But you can’t rely on that alone. Depending on the species of starfish you have, you will probably need to feed them shellfish. Mussels, clams, oysters, snails, and even scallops are great food options. If you have hairworms, these can also be included in their diet!

Author’s note: When buying these foods for your starfish, it’s important to make sure you’re buying them from a reputable source. Also, be sure to clean them thoroughly before placing them in your aquarium! Not only can unwanted chemicals be a problem for your starfish when it eats these foods, but other creatures in the tank could suffer as well.

If you want to mix things up a bit, consider adding leafy greens to their diet as well. Kale, spinach and lettuce are common options. Be sure to boil them before feeding them to your starfish.

How often should you feed them?

Now that you know what starfish eat in a home aquarium, it’s important to cover their ideal feeding schedule.

Although this may vary slightly depending on the species you have, a good rule of thumb is to feed your starfish once every two to four days. This window of time will take into account their digestion timeline and other variables that might impact their hunger levels (like having more seaweed than normal to eat recently).

A brittle starfish on the sand

To tell if your starfish is hungry and ready to eat, simply place food next to it and watch its reaction. If they clearly decide to investigate and consume the food, they are likely hungry and ready to eat. If they don’t show interest, now is probably not the time.

Some aquarists like to feed their starfish at night, as these critters are nocturnal. However, others like to let them gradually adjust to their diet during the day.

How their diet varies by species

In the sections above, we’ve covered what starfish eat in most situations. But that being said, the species you are dealing with will dictate the specific diet you want to provide.

Here are the diets of some common species:

  • Chocolate Chip Starfish: Sea urchins, snails, crustaceans, shrimps, algae and tubeworms. They will also eat coral (so be aware of that)
  • Brittle Starfish: Small invertebrates like shrimps, snails and crabs.
  • Starfish Asterina: Algae, corals, silkworms, biofilm and detritus.
  • Marbled Starfish: Detritus, seaweed, pieces of shrimp, fish flake food.
  • Starfish Sifting Sand: Small crustaceans, molluscs, silkworms, feeder shrimp and detritus.
  • Panoramic Starfish: Coral, shrimp, snails, seaweed and sometimes other starfish.
  • Linckia Starfish: Algae, detritus, biofilm, food flakes.

The importance of knowing what species you have

Knowing what type of starfish you have is extremely important, and it’s easier to make a mistake here than you might think. Some of the common species that people keep as pets look very similar and are mislabeled by their local pet store.

This means that even if you think you know what your starfish is eating, you don’t. This could result in the introduction of a starfish into your aquarium that attacks your coral, and even other aquarium inhabitants!

So believe us, spend a little more time checking the cash you are getting. It’s not worth the potential headaches if you get it wrong.

Do starfish eat algae?

Starfish eat algae, but their interest will vary depending on the type of species you are dealing with.

For example, if you have an Asterina starfish, the seaweed will be eaten on a fairly regular basis (and will actually make up a reasonable part of their diet if available to them).

On the other hand, a chocolate chip starfish will need other food sources to survive. Although it will likely eat any algae it encounters, that will not be the primary focus of its diet.

Do starfish eat shrimp?

Some starfish will eat shrimp if they manage to catch it. Brittle, chocolate chip, and marbled starfish are all examples of species that will happily munch on these crustaceans when they can.

This means that if you have shrimp in your aquarium that you would like to keep, avoid carnivorous starfish that are large enough to eat them. Despite their slow and stealthy nature, starfish are effective predators!

Do starfish eat coral?

This is another popular question when it comes to what do starfish eat, and understandably so. Maintaining healthy corals in your aquarium can be difficult, and it can be a source of great pride for many aquarists.

And unfortunately, some starfish eat coral. This means that species like the asterina or the panama starfish are probably a bad choice. They obviously don’t do it maliciously, they just do what you would do if you saw a tasty snack in front of you!

Final Thoughts

We hope this guide to what starfish eat (and how they do it) will make it easier for you to decide which species is right for you. Remember, it’s essential to spend a little extra time checking out the type of starfish you’re actually getting. You don’t want to introduce one that is wreaking havoc on your aquatic community!

If you have any questions about starfish diets or the foods they eat, send us a message. We are more than happy to help!

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