What do Hermit Crabs Eat in a Saltwater Tank?

In a saltwater aquarium, hermit crabs are valued inhabitants primarily for their scavenging habits, playing a key role in tank cleanliness by consuming available food sources.

Saltwater hermit crabs mainly eat **uneaten food** and graze on certain types of **algae** present in the tank environment. They are often added to reef aquariums specifically to help manage these food sources.

Based on common practices and information regarding their diet:

*   **Uneaten Food:** Hermit crabs actively scavenge for food particles that have been missed by fish or other tank inhabitants. This includes leftover fish food, invertebrate pellets, and other decaying organic matter.
*   **Algae:** They are known to graze on algae. However, it's important to note that while they help control some algal growth, they are particular about the types they consume. According to the provided reference, hermit crabs predominantly graze **green nutritious algae**. They do *not* typically consume the difficult "big three nuisance algae types."

Here's a quick summary of their primary diet components in a saltwater tank:

| Diet Component           | Description                                     |
| :----------------------- | :---------------------------------------------- |
| **Uneaten Food**         | Leftover fish food, pellets, decaying matter.   |
| **Green Nutritious Algae** | Specific types of algae they actively graze on. |
| *Not Typically Eaten*    | The "big three" nuisance algae types.           |

Their natural scavenging behavior makes them effective members of a cleanup crew, helping to keep the substrate and live rock free of excess food and certain types of algae.