What Do Crabs Eat and How to Feed Them?

Owning a pet land crab or aquatic crab can be a very worthwhile and unique experience. So, if you are looking to keep them as pets, it is important to do research on how to take care of them and how to feed them.

Generally, crabs are omnivorous and opportunistic feeders. They will eat just about anything they can get their claws on. It can be detritus, animals, and plants, either living or decomposing.

I am saying “generally” because they’re more than 4500 different species of crabs in the world and about 50 species that are heavily traded in the aquarium hobby. Each species has its own feeding requirements. In addition, their feeding preference may change depending on the age and the molting cycle. 

In this article, I will highlight the various food sources available to crabs for consumption, and how often they should be fed in captivity.

What Do Crabs Eat in The Wild?

Most crabs are foraging omnivores. They will eat plant and animal matter that they come across. Basically, it means that they will eat anything left unattended on the ground, as they are scavengers.

At the same time, certain species and even families show tendencies towards a more specialized diet.

For example, Portunid crabs are reported as being mainly carnivorous, feeding on many organisms, particularly on slow-moving invertebrates such as molluscs, snails, slugs, worms and crustaceans (including other crabs up to their own size).

Some terrestrial crabs of Sesama family are common herbivores. They feed on a variety of plant materials as well as on decaying organic matter, like: leaves, plants, flowers, belowground rhizomes, fruits, vegetables, barks, seeds, grains, etc.

What Do Crabs Eat In The Aquarium?

A simple fact most crabs are not fussy eaters by nature does not mean that we can give them whatever we like or that we should not care about their diet.

This approach will only lead to diseases and problems with their exoskeleton.

So, if we want to give them the best life possible, we need to provide them with a well-balanced diet. By doing so, crabs will get all necessary microelements, vitamins, and minerals that are needed for their body to function correctly.

That is why it is very important to understand that they need to have a varied diet of: 

• Vegetables and Fruits
• Protein
• Calcium

Important: Terrestrial, semi-terrestrial, and aquatic (freshwater and marine) crabs should be fed differently. We have to understand some limitations. For example, in the aquarium, I would avoid all citrus fruits, tomatoes, avocado, etc. These foods contain a lot of sugar and can cause a bacterial bloom in your tank. As a result, it can also lead to depletion of oxygen and/or even lower pH in your tank. Another problem is that most of the fruits are too messy. It can be even worse in marine tanks. So I would never recommend using fruits in marine tanks. At the same time, you will not have such problems with terrestrial and semi-terrestrial crabs in paludarium and terrarium setups. You can also read my article “Difference between Aquarium, Terrarium, Riparium, and Paludarium?”.

Recommended Food for Crabs

Vegetables

• Asparagus     
• Alfalfa
• Basil   
• Broccoli         
• Beet   
• Carrots           
• Clover
• Corn   
• Cabbage of all sorts 
• Cucumber     
• Cauliflower   
• Green beans 
• Green pea     
• Leeks
• Lettuce           
• Moss 
• Nettle
• Oats (soaked and mashed) 
• Pumpkin
• Peas
• Parsnip         
• Plantain (broadleaf)   
• Pepper (only sweet)
• Swede
• Sprouts
• Turnios
• Watercress
• Zucchini

Fruits

A variety of fruits your crabs will enjoy.

• Apples
• Apricot
• Avocado                   
• Banana                     
• Blackberries
• Blueberries               
• Butternut squash                   
• Cherry           
• Coconut                                           
• Dragon fruit
• Grape and Raisins               
• Mango
• Melon
• Nectarines
• Olives
• Papaya
• Pear
• Plum
• Peach
• Physalis
• Raspberry
• Strawberry
• Sharon fruit
• Satsuma
• Tangerine
• Watermelon

Note: Most fruits need to be peeled (even grapes, plums, etc.).  You can also cut them into small pieces so the crabs can eat them easily.

Protein Food

Generally, crabs need a lot of protein to grow and in the absence of food, they can start cannibalizing fast.

Based on different experiments and observations, in many crab species, the maximum growth can be achieved in the 20-30% protein diet.

Keep in mind that there are two types of protein:

• animal-based,
• vegetable-based.

Even though, in terms of components, we will not see a big difference between animal and plant proteins, the ratio of amino acids is different. That is why crabs need all types of protein. Diversity is very important!

The following are suitable food items for your pet crab:

• Beef (raw, or boiled)
• Chicken (raw or boiled)
• Pork (raw or boiled)
• Fish (raw or boiled)
• Shrimp (raw or boiled)
• Brine shrimp
• Blackworms
• Bloodworms
• Grindal worms
• Cockroaches
• Crickets
• Krill (freeze-dried)
• Snails (crushed)
• Mosquito larvae
• Eggs (including shells)

Calcium

Calcium is super important for any crab species because this is the main component of their exoskeleton (shell). For example, their exoskeleton comprises up to 50% of dry weight and is mineralized with calcium carbonates and magnesium.

A calcium deficiency can cause weakness in the shell and when this happens, the crab becomes susceptible to diseases, heat, and dehydration (in terrestrial crab species).

Calcium can be found in such products as:

• Kale,
• Broccoli,
• spinach,
• Seaweed,
• Figs,
• Nuts,
• Cuttlebones,
• Eggshells,
• Wonder shells,
• Oyster shells,
• Seeds,
• Insects (carapace),
• Mollusks (shells), etc.

Cuttlefish bone should be in the tank all the time. 

Plants

Be very careful with plants in crab tanks.

I’d say that there are only a few species that are safe to keep in planted tanks (for example, Pom Pom Crabs, Vampire crabs, Thai Micro Crabs). So, do your research beforehand!

In all other cases, there is a huge risk that plants will become their delicacy. Unfortunately, many crab species will eat, cut, and uproot any plant in the tank.

Therefore, unless you are ready to buy some cheap plants you are willing to lose, it will be better to focus on floating plants or fake plants.

Commercial Diets

In captivity, the crab’s diet should also include a balanced commercial food supplement with a variety of fresh foods and treats.

As with all crustaceans, ideal food sources include popular dry pellet foods and frozen foods. These are commercially prepared, high-quality foods that contain high amounts of protein & vitamins.

Good examples of these are (links to check the price on Amazon):

• API Fish Food flakes,
• Dennerle Shrimp King Cambarellus,
• Tetra ShrimpWafers,
• Frozen blood worms,
• Shrimp pellets
• Shrimp Granules
• Hikari Shrimp Cuisine, 
• Hikari Tropical Crab Cuisine.

Crabs may really like salty, fatty, or sugary snacks such as chips, and sweetened cereal but these should be avoided.

How Often and How Much Should You Feed Crabs?

In general, most adult crab species do quite well on one feeding per two days. However, some owners prefer to feed them daily to prevent them from getting hungry and picking on tankmates.

However, young crabs should be fed every day. They grow fast and require frequent feeding. The good thing though is that young crabs will eat the same meals as adult crabs.

The amount of food required for each crab is up to 5-10% of its weight.

Of course, nobody will do such calculations, that is why the optimal dose is usually determined empirically. So, ensure that the pieces of food served are no more than 1/2 of the crab’s body.

Crabs are not fast eaters. Leave their food in the tank for 10-12 hours before removing it.

Optimal Feeding Time

In nature, crabs are nocturnal animals. Their feeding activity increases at night (a few hours after the onset of darkness). Even though some individuals can be active even in the daytime.

For best results, give them food before nightfall. It will replicate the conditions and environment under which they eat naturally.

Food Variations

A wide variety of foods from the list above should be offered on a rotating basis.

DO NOT feed them the same food all the time. This is wrong.

Ideally, you need to have at least 2-3 different types of products to vary. It will give your crabs more vitamins to improve their immune system and prevent molting problems.

Crab Species and Diet Preferences  

Fully aquatic freshwater Crabs	Diet	Temperament	Plant safe
Thai Micro Crab	Detritivore /omnivore	Peaceful	Yes
Pom Pom Crab	Omnivore / Algae eater	Peaceful	Yes
Matano Crab	Omnivore / Carnivore	Aggressive / Territorial	No
Panther Crab	Omnivore / Carnivore	Aggressive / Territorial	No
Saltwater crabs	Diet	Temperament	Сoral safe
Arrow crab	Mostly Carnivore / Omnivore	Semi-aggressive	Yes, with caution
Porcelain Anemone crab	Mostly Carnivore / Omnivore	Peaceful	Yes
Sally Lightfoot Crab	Omnivore	Semi-aggressive	Yes
Boxer Crab	Omnivore/Carnivore	Peaceful	Yes
Emerald crab	Omnivore	Slightly aggressive	Yes, with caution
Semi-aquatic crabs and terrestrial crabs	Diet	Temperament	Plant safe
Red claw crab	Detritivore /omnivore	Aggressive	No
Fiddler crab	Detritivore /omnivore	Slightly aggressive	No
Red Apple Crab	Mostly herbivore /omnivore	Slightly aggressive	Yes
Marble crab	Mostly carnivore/omnivore	Slightly aggressive	Yes
Vampire crab	Omnivorous	Peaceful	Yes
Tangerine-head crab	Omnivorous	Peaceful	Yes
Halloween Moon Crabs	Mostly herbivore/omnivore	Aggressive	No
Rainbow Crab	Omnivorous	Aggressive	No

How do Crabs find their food?

Although crabs have compound eyes, which give them panoramic vision, when it comes to feeding, they mostly rely on their antennae and antennules also called “feelers” (read more about crab anatomy here).

Their antennules have special chemoreceptors that allow them to detect chemicals in the water that are released by the food. By using their pincers, they pass food to their mouths which have 3 pairs of maxillipeds (jawfoot) and a mandible (jaw).

Crabs use maxillipeds to rummage, hold and bring food to the mouth during eating. Unlike humans, their jaws open by moving from side to side.

Interesting fact:  Do you know that crabs have teeth inside their stomach? It is called the gastric mill apparatus which functions in mastication (cutting and grinding) as a prelude to further digestion.

In Conclusion

If you decide to keep crabs as pets, it is really important to know what they eat. Because crabs live in many different places, their diets vary depending on their environment.

While the most commercial diets are very convenient and are well balanced, they should be supplemented with other foods as well.

Make sure that they have a good variety in their menu. It will make them happy and healthy.