Hermit Crabs in Marine Tanks | Care Guide

Ever since I had the privilege of seeing those telltale trails on the sand on the white sandy beaches, I know that I have wanted to own a Hermit Crab. Not only are they great to watch for amusement as they rummage around the substrate and rocks, they actually serve a greater purpose for maintaining a clean tank.

In this article, we are going to look at how to care for these fascinating creatures and why you should seriously consider adding them to your tank (if you haven’t already!). Also note we are looking specifically at the Green Striped Hermit Crab. There are a large variety of hermit crabs that can be found at your Local Fish Store (LFS). A lot of the care guidelines detailed in this article will be generally applicable to other species of hermit crabs, however you should also do your due diligence and research specific care instructions for the type of hermit crab you are interested in.


Green Striped Hermit Crabs can be found in and around coral reef systems located around the Caribbean.  They can also be found in the waters around the Gulf of Mexico. 


source: reefcleaners.org

Probably one of the most interesting features about Hermit Crabs is that they inherit abandoned (and sometimes not abandoned) shells. Throughout it’s life you will probably only see the Hermit Crabs claws, a few feet, beady eyes and it’s waving antennae.  However if you are lucky, you may be able to catch a brief glimpse of the Hermit Crabs body as they switch between shells.

The coloration of the Hermit’s claws and legs can vary between species, however for the Green Striped Hermit Crab you will see greenish to dark green stripes on the claws and feet.


little crab
Source: Unsplash

Hermit Crabs are a proud member of the clean up crew. This means they will forage and scavenge on uneaten foods around the tank that the resident fish have missed during feeding time. This is particularly handy in keeping your water parameters in check and your tank doesn’t become toxic with ammonia or nitrite.

Hermit Crabs will also graze on algae growing in your tank and pick their way across live rock and corals.


Description Specification
Difficulty Easy
Personality Docile
Size 2 inches
Diet Omnivore
Tank size At Least 20 Gallons
Tank type Marine
Reef Safe Yes

Hermit Crabs are considered a good animal to begin with for reefers starting in the hobby as they are tolerant of less than ideal water conditions.  As such they do not have any specific requirements (unlike other fish and corals) to live a long a happy life.

The main thing to remember is to maintain regular water changes and testing your water parameters. Also feed your fish a variety of foods and the leftover uneaten food will make it’s way down to the bottom of the tank where the hermit crabs will scavenge their meals.

Things to consider for Hermit Crabs

Do they kill snails?

One of the main concerns with reefers considering adding Hermit Crabs to your tank is whether they will kill other inhabitants, particularly snails.

In general, the answer will be a no.  However there are certain things you can do to discourage the practice of killer Hermit Crabs. As your Hermit Crab grows it will inevitably look to move home. This means if there are no other abandoned shells lying about the tank, it may resort to killing snails for their shells. To prevent this, ensure you have enough shells of varying size lying on the bottom of your tank. By doing this you will give the Hermit Crab amble options and it won’t have to even consider looking at those snails on the walls and live rock.

Just to show you that it does happen here is a video of a poor snail being preyed on.

Mixing Hermit Crab Species

Another thing to consider is whether or not to mix different species of Hermit Crabs in the same tank.   Unfortunately there is no definitive answer to this question. With so many species of Hermit Crabs and the different types of personalities within the same species, you will never be able to confidently same yes or no.  In general you should probably stick to one type of species, as the likelihood of every crab co-existing peacefully is higher than two or three different species living together. The reason for this is because if food becomes scarce in the tank, it is natural for one species to attack another for food and to eliminate the competition.


I highly encourage all reefers to include Hermit Crabs in their tank. Not only do they help with breaking down uneaten foods and facilitating the nitrogen cycle. They are quite amusing to watch climb around the tank.

The few things to look out for is if you have snails, they may prey on them if they need a new home. Also try not to mix species of crabs together, as having one versus more than one species in the tank will likely result in a more peaceful tank habitat.

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