Freshwater Crabs for aquariums

Freshwater Crabs for Aquariums

It’s easy to assume that fish tanks are, well, just that – tanks for fish. However, as you start getting into the aquarium owning hobby, you’ll likely find that there are more than a few interesting critters you can safely introduce alongside the odd freshwater fish, too.

For example, have you ever considered taking a look at adopting freshwater crabs for aquariums?

Yes – there are some crabs out there which you can safely introduce into your home tank or aquarium.

Crab in fishtank

It might not be a beginner’s route towards setting up a home tank, but there are lots of different types of crab out there who will gladly become part of your own aquarium space. That is, providing you look after them properly!

This guide is a quick introduction to crabs that you can introduce to your freshwater tank alongside other creatures.

Remember that not all marine life will be friendly with one another, so make sure to do a bit of research and to hunt down a few snippy critters that are likely to live long and healthy lives alongside your tropical fish!

Are there any fully aquatic freshwater crabs?

Yes – there are more than a few crab species which are considered ‘fully aquatic’, or happy to spend their days underwater.

However, ‘fully aquatic’ can also mean that your crab needs to come up to the surface every once in a while to breathe, meaning you absolutely must prepare a tank so that surfacing is easy.

It’s a really good idea to take a look at which crabs are considered aquatic, freshwater, and which will live happily alongside fish and other creatures in your tank.

As always, it makes sense to both do a little homework and to consult an expert at your local aquarium center to learn more.

However, this guide will certainly support you as a fantastic way to start setting up aquatic crabs for your own home tank.

Do freshwater aquarium crabs need air?

Some will, and some won’t – it really does depend on the species.

There are a handful of aquatic crabs who can healthily live underwater without the need to ever come up for air.

However, most crabs based in fish tanks or underwater will need a form of escape route, or a system of holes, so that they can easily scuttle in and out from time to time. It’s always a good idea to try and make their homes as flexible as possible.

Before you assume whether or not your crab needs to get to the surface occasionally, make sure to check up care tips for your species and ensure that you have the best tank facilities available.

Be ready to change the water and to check the levels as often as you might for your fish, too. A lot of this is purely down to common sense!

How big do freshwater crabs get?

Again, this can depend on the type of freshwater crab or aquatic crab you adopt. On the whole, though, you can expect a freshwater crab that lives in a tank to grow up to four inches in length.

Some are tiny, however, and never grow any bigger than one inch in size.

Man holding Fiddler crab

Therefore, it’s a really good idea to swing more towards setting up a tank that has more space than a little.

A smaller tank is going to help your crabs to feel that bit more cramped, and it’s certainly not going to do your fish any good, either.

Make sure to check out the expected growth patterns for your crabs before you set them up properly. If you are introducing them to an existing tank, try and narrow down your search.

If the main focus of your new tank will be aquatic crabs, then it makes sense to go for a bigger size wherever possible.

How long can freshwater crabs stay underwater?

Freshwater crabs can stay underwater for various periods of time. The crabs you’ll see on the beach won’t need to go under the surface – in fact, submerging may well kill them – meaning that you’ll get some who will need to spend a little time in and out of the water.

Beach crabs and those you’ll see out of the sea really only need moist gills to survive.

Truly aquatic crabs, however, will have gills like your average fish – meaning they will live underwater permanently.

Again, the time your crabs spend underwater really depends on the type and species you adopt.

This is why it is so important to spend time researching the different species and to see which will fit your ideal home tank the best.

The Best Types of Crabs for Your Freshwater Aquarium

Ok – let’s cut to the chase. Here are a few of the fantastic aquatic crabs you can adopt right now, and which will happily live in your own home freshwater ecosystem.

As mentioned, this is just a quick introduction to some of the more curious and exciting types of scuttler out there – don’t be afraid to do a little more digging if you’d like to know more!

Fiddler Crab

Fiddler Crab
Fiddler Crab

The fiddler crab is a semi-aquatic creature, which means it has super-powered breathing – it can live in and out of water! These crabs generally grow to about two inches in length, and there are actually many different species.

They tend to be pretty calm though maybe a little feisty with other males in the species, meaning it’s always a good idea to keep a close eye on them in case they get into any fights.

Fiddler crabs generally thrive well in mid to large tanks, starting at around 15 gallons. Fiddlers don’t do well in smaller tanks as they can feel stressed out if conditions are too tight.

Perisesarma bidens

Red clawed crab
Perisesarma Bidens, Red Clawed Crab

The Perisesarma bidens is generally called the Red Claw Crab. It’s a semi-aquatic critter that hails from Asia, and unlike the fiddler crab, this best will need access to land every now and then.

They will likely need something akin to a basking dock with substrate when they want to get out of the water.

There are a couple of things you should keep in mind before you adopt Red Claw Crabs for your tank.

Firstly, they can be very aggressive and extremely territorial. It’s therefor a good idea to try and house them on their own. Secondly, they are not ‘freshwater crabs’ by definition – they can live in these conditions, but it’s not their main habitat.


Geosesarma Vampire Crab
Geosesarma Vampire Crab

This scary-looking critter goes by the appropriate English name of the Vampire Crab! Like the Red Claw Crab, Vampires will need access to land occasionally, meaning setting up a palladium they can access easily is a really good idea.

They aren’t actually as scary as they seem. Geosesarma tend to hide away a lot, making them some of the shyest of crabs you can find for your freshwater tank.

Perhaps the vampire name comes from their love of the dark – not so much their frightening looks!

Ptychognathus barbatus

Pom pom crab
Ptychognathus barbatus, Pom Pom Crab Source

Ptychognathus barbatus has the catchy name of Pom Pom Crab in English – and these are actually different species to the ones you find out in saltwater, so do adopt them carefully.

Freshwater Pom Pom Crabs are actually pretty mysterious. They are friendly and leave other creatures well alone and will generally grow up to an inch long.

They tend to enjoy neutral waters. What’s notable about this crab is that while it can live entirely underwater, it’s still going to try and escape! Don’t give it that opportunity, as they are absolutely tiny!