If you have ever seen a crab on the beach, you probably noticed that they are always scavenging for food. But do they specifically hunt down and eat algae?

Some species of crabs, such as the Dwarf Blue Leg Hermit, do eat algae. As frequent visitors to shallow water habitats such as rock pools around fishing ports, blue rock crabs are another species that consume algae.  Other species of crab that eat algae include the brown shore crab, the green shore crab, and the marbled rock crab.

It is, however, unclear if crabs only consume the plant as a nutrient for growth or something else that we may not know about yet.

In a study published in the journal Marine Biology, researchers found that algae is an important part of a crab’s diet and can make up as much as 25% to 50% of their total intake. These findings indicate that herbivorous crabs may represent key players in seagrass ecosystems by consuming the plants while simultaneously limiting encroachment by other plant species.
So yes, crabs do eat algae and in large quantities!

Do crab eat algae

Crabs will use their claws to scrape off the algae from rocks, and then they’ll take some of this film with them onto other parts of the rock to feed on it.

It’s possible that eating these plants could help crabs grow faster since many species are omnivores. It’s also important to note that crustaceans require both animal protein and vegetable matter, so scavenging might very well provide an all-around balanced diet for crabs. As long as food sources are abundant near where they live, crabs can find a variety of nutritious foods to eat.

Why Do Crabs Eat Algae?

Algae-eating crabs, such as the hermit crab, particularly like this meal because it’s natural, easy, and non-resistant. Hermit crabs will spend much of their time in rock pools on the shore, feeding on algae that grow among the rocks and drinking from water droplets left by waves crashing against the shoreline.

Crabs also like to eat little, but often. So the plentiful algae meal presents the best option that is always available. Also, algae don’t require much chewing, making them a good snack that is easily consumed.

Some scientists had suggested the crabs’ willingness to consume smaller quantities of more nutrient-dense foods such as algae may be an adaptation for survival during periods when other sources either dried up or became less plentiful.

Which Types of Algae Do Crabs Eat?

Crabs feed on a variety of algae species, including:
Bubble algae
-Brown algae
-Green hair algae
-Red slime algae
-Coralline algae, among others.

Can Crabs Survive on Just Algae?

Crabs such as the hermit crab may survive but can’t flourish, feeding on algae alone. Repeated feeding on algae can cause the crab to develop an imbalance in its calcium levels. Algae also lack protein, which is one of the most important nutrients for all animals. Finally, if there is no other food sources available, crabs may deplete their energy reserves by eating too many algae at a time.