Tiny Tenants: A Guide to Marine Hermit Crabs for Your Reef Tank

In this guide

Tags: hermit crabs, reef tank cleanup, blue leg hermit crab, scarlet hermit crab, marine invertebrates

Hermit crabs are usually one of the first invertebrates added to a new marine tank, and for good reason. They are inexpensive, constantly active, and genuinely useful for keeping algae in check. Watching one investigate a new shell, testing it with its claws before committing to the move, is one of the small pleasures of the hobby.

Popular species for a reef tank

• Blue leg hermit crab, the classic choice, small, hardy, and a relentless algae grazer that works well in groups
• Scarlet reef hermit crab, similar in size with striking red legs and a bright yellow face
• Electric blue hermit crab, larger and more strikingly coloured, prized for its vivid blue legs but occasionally reported nipping at large polyp corals or turbo snails
• Halloween hermit crab, an ornamental species with a bold striped pattern, kept more for looks than for cleanup work

The one rule that prevents most problems

Hermit crabs do not grow their own shells, they borrow them, and a crab that outgrows its shell without a replacement nearby will attack snails to steal theirs. Keeping three to five empty shells of varying sizes in the tank at all times prevents almost every reported case of hermit crab aggression towards snails. Marine specialist shops in India do not always stock spare shells separately, so it is worth asking your dealer to set some aside, or picking up clean, empty shells from a beach trip and boiling them thoroughly before adding them to the tank.

Care basics

• Stick to small species for a reef tank, since larger hermit crabs can become opportunistic towards corals and slow moving tankmates
• Avoid copper based medications entirely, since hermit crabs, like most invertebrates, cannot tolerate them
• Acclimate slowly using a drip method, since sudden salinity changes are harder on invertebrates than on fish
• Feed sinking algae wafers occasionally if the tank does not have enough natural algae growth to sustain the group

A well stocked hermit crab crew, matched to the tank's size and given enough spare shells, tends to run quietly in the background for years, one of the lowest maintenance and most reliable workers in a reef system.

Article content © Ravi Teja. All rights reserved.