Measure Shell Openings

It is important to choose shells with the correct opening size for your hermit crabs. The opening size you choose should be 1/8" bigger than your hermit crab's big claw. You should measure the length of the largest claw, not how wide it is.

Hermit crabs use their biggest claw as a trap door. Their claw should be recessed just inside the opening. If their big claw is down inside, the shell may be big enough or possibly a little too big depending on how deep the claw is in the opening. If the claw is too big to recede within the opening, your crab definitely needs a larger shell.

A good rule of thumb is to buy shells with an opening that's 1/8" larger than your hermit crab's big claw.

How we measure the openings of our shells.

Measure a Round Opening

Round Opening seashells are measured side to side.

Measure an Oval Opening

Oval opening seashells are measured by picturing an oval.

Give your hermit crab a little variety! If you present your crab with a few properly sized shells to choose from he or she is much more likely to find a comfortable match. You should have at least three shells for every crab in your tank. This will also help to prevent ugly shell fights.

Author: Amy Ferguson