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Maybe you like the way shrimp flutter through the sea, or the way hermit crabs scuttle along the beach.
Maybe you like the way either shrimp or hermit crabs look or act, and think they’d make good pets.
Maybe you love the way the two taste together on a seafood platter.
But while you’re hopefully not interested in purchasing them for the latter point, the question remains – can you keep both shrimp and hermit crabs together, and do they actually get along?
A Quick Look at Both Species
Before we see how shrimp and hermit crabs do together, let’s briefly look at them on their own. To keep crabs, shrimp, or any kind of sea life for that matter, you need to check the tank compatibility.
For starters, though shrimp may be tiny, they need a big tank. The smaller the tank, the more likely water parameter fluctuations are, which can wreak havoc on shrimps’ health.
On the other hand, there is such a thing as a tank being too big, with 20 to 29 gallons being ideal. You’ll also need to make sure that the filter you use in your aquarium isn’t so big as to be able to shuck the shrimp up into a horrible fate.
Heating-wise, freshwater shrimp tend to prefer moderate water temperatures of around 70 to 79 degrees Fahrenheit. Planting plants and other substrates are also essential to give them hiding places.
Hermit crabs also like to have hiding places though, despite their name, they actually like having a friend or two around. You should thus ideally have a couple crabs in your tank.
They can grow up to six inches long and prefer to live on sand. That means that any tank that includes both shrimp and hermit crabs are going to need a sandy area for the crabs to make themselves at home.
Crabs love to put those strong claws to work by digging and burrowing, so you’ll want to make sure that the sandy substrate you supply them is at least three times deeper than the height of their body. Don’t use carbon carbonate, as this does not retain moisture and can stick to your crab’s legs – which, as we’ll see, could be a problem.
Crabs like a fair amount of humidity, between 60% and 80%.
How They Interact
Like shrimp, hermit crabs tend to prefer to have a lot of space, at least 10 gallons. That said, since they do better in groups (and you’d need a bigger tank for keeping shrimp anyway), you’re probably better off with the aforementioned 20-gallons-and-up approach.
Since your hermit crab is going to want a lot of sand, you’ll need to plan the layout carefully to ensure that they have enough land and your shrimp have enough water.
While they may not “fight” over hiding places, you’ll also want to make sure that there are enough spaces for both of them.
Additionally, shrimp’s shells are sometimes made in large part of calcium carbonate – the very substance that can stick to crabs if you’re not careful.
Will that actually happen?
Will anything bad happen when you mix these two together?
Well, it’s honestly hard to say with any kind of unifying certainty. Unlike other tank combos, there is no single answer to how well shrimp and crabs may get along together.
One reason for that is that reducing this down to “just” shrimp and “just” crabs is disingenuous. By some estimates, there are more than 2,000 species of shrimp in the world, and more than 6,700 species of crab.
There are thus literally tens of thousands upon thousands of potential shrimp/crab pairing combinations, some of which may work far better than others.
For example, blue hermit crabs are pretty peaceful creatures, and typically get along fine with skunk cleaner shrimp. On the other hand, there are many reports of emerald crabs turning tyrant and pinching and killing poor shrimp in its claws.
That said, other shrimp species such as mantis shrimp can hold their own against crabs, sometimes even attacking them.
Part of the broader problem here is that crustaceans don’t have any shame over cannibalism. They’ll eat members of their own species, let alone a fellow crustacean of a different species, meaning the wrong combination could leave your shrimp or crab licking their chops (or they would if they had a tongue).
So What Can You Do?
However, there are still plenty of shrimp-crab combos that can work. It’s just a matter of finding which crabs do well with which shrimp.
Unfortunately, the aforementioned vastness of both groups is a blessing and a curse here.
On the one hand, with so many variations, there are plenty of chances for you to get a shrimp and a crab that can coexist peacefully.
On the other hand, all those variations also means that it’s going to be hard to nearly impossible to Google search every potential pair and see if someone’s written about them as a pairing.
Thankfully, even if you aren’t lucky and can’t find an article written about the specific pairing you’re considering, you can fall back on some tried and true tank mate tests.
First and foremost, you need to know what both species eat. Ideally, they should both be happy eating algae or plants so as to avoid any “carnivorous thoughts,” which might lead to trouble.
A lot of species of crabs and shrimp are omnivorous, supplementing their algae intake with mealworms. That may be fine, but if either party enjoys eating anything “bigger” or “meatier” than that, chances are it’s best not to pair them up.
Even if you do feed them mealworms, however, you probably shouldn’t make them “compete” for their food, lest competition lead to cannibalistic fighting. Make sure there’s more than enough mealworms to go around.
You’ll also want to be sure to spread the food around the tank. Remember, crabs especially like to stake out places where they can retreat to themselves, so shrimp popping by to eat food in their territory is probably a bad idea.
Then there’s the issue of size.
If one party is way smaller than the other, it may appear less like a tank mate and more like a snack.
“Expanding” on the issue of size, the bigger your tank when keeping both shrimp and crabs, the better.
The more space your hermit crab has to carve out its own territory, the more tolerant it’s bound to be of its fellow tankmates, including shrimp.
Remember that there’s also safety in numbers, and both crabs and shrimp like at least a couple members of their own kind as compatriots. If you have a bunch of crabs versus one shrimp, or vice versa, the outnumbered party may feel understandably vulnerable.
Finally, a mixture of smaller crabs and dwarf shrimp may be your best bet at harmony.
While larger shrimp and crabs can take care of themselves better, they can also pose a bigger threat to one another. By contrast, micro crabs are typically peaceful and too small to do serious damage, and the same goes for dwarf shrimp.
In short, some hermit crabs and shrimp make for problem combos, and others make for great tank mates. Decide which specific species of each interest you, and do whatever research you can on them individually and their potential pairing before buying.