A lot of people are excited to learn that these strange and unorthodox creatures can also be kept as pets. Of course, this is great but … can we keep crabs with fish, shrimp, snails, or even other crabs in our aquariums? Can crabs co-exist peacefully with other tankmates? Recently, I have got several questions, so I decided to summarize my thought regarding these questions.
The answer is, yes it is possible to keep some crab species in a community tank. That is why it is crucial to know everything about your crab species and its potential tankmates.
Without this information, it can be hard to predict their compatibility.
There are many crab species in the aquarium hobby. Depending on the species, some of them can extremely aggressive while others may only behave defensively or prefer to run and hide instead of fighting.
Any mistake and despite the fact that crabs can be a ton of fun to own, the ‘wrong’ crab species can also turning your beautiful community tank into total chaos, and destruction.
Touch Me If You Dare
When we look at a crab, it is pretty easy to take immediate note of their claws. These claws are not for nothing!
Most crab species, despite their size, are quite territorial in nature. They will defend their homes and threaten each other if they come too close to each other.
Crabs are also extremely opportunistic eaters. However, some of them are not just excellent scavengers but predators and able to catch a delicious meal with absolute ease.
Therefore, while they might be small and cute, a crab is actually a pretty big threat in a tank setting. They have a pretty good reaction and have a tendency to react defensively.
It means that even when they cannot kill a bigger fish, they may not hesitate to take chunks of fins if they feel threatened. I assure you, their claws can do some very serious damage!
List of Most Popular Aquarium Crabs and Tankmate Compatibility
| Temperament | Fish | Dwarf shrimp | Snails | Their own kind | Other crab specie | |
| Red claw crabs (Perisesarma bidens)
Size 10 cm (4 inches) |
Aggressive | No | No | No | No (only with females) | No |
| Thai Micro Crabs (Limnopilos naiyanetri)
Size 2.5 cm (1 inch) |
Peaceful | Yes | Yes | Yes | Yes | No |
| Pom Pom Crab (Ptychognathus Barbatus)
Size 2.5 cm (1 inch) |
Peaceful | Yes | Yes | Yes
(can attack very small snails) |
Yes | No |
| Vampire crabs (Geosesarma dennerle)
Size 5 cm (~2 inches) |
Peaceful | Yes | Yes
(can attack very small shrimp) |
Yes
(can attack very small snails) |
Yes | No |
| Tangerine-head crabs (Geosesarma krathing)Size 4 cm (~1.6 inches) |
Peaceful | Yes | Yes
(can attack very small shrimp) |
Yes
(can attack very small snails) |
Yes | No |
| Panther Crab (Parathelphusa pantherine)Size up to 12 cm (5 inches) |
Aggressive | No | No | No | No (only with females) | No |
| Matano Crab (Syntripsa Matannensis)Size up to 12 cm (5 inches) |
Aggressive | No | No | No | No (only with females) | No |
| Rainbow Crabs (Cardisoma armatum)
Size up to 15 cm (6 inches) |
Aggressive | No | No | No | No (only with females) | No |
| Fiddler crab (Uca sp.)Size 6 cm (~2 inches) |
Semi-Aggressive | No | No | No | No (only with females) | No |
| Halloween Moon Crabs (Gecarcinus quadratus)Size up to 6 cm (2.5 inches) |
Aggressive | No | No | No | No (only with females) |
Crabs and Potential Aggression
As we can see, most popular aquarium crab species are an obvious threat to fish, shrimp, snails, or even other crabs in your community tanks, but the reality is that they might also not catch anything.
We can also hear some stories about how some aquarists could keep crabs without many problems. This is also one of the reasons why so many people consider the idea that it might be fine to bring a crab into their community tank.
I strongly believe that this is probably not the best course of action. If it works for them it does not mean that it will work for you!
Interesting fact: Keep in mind that fish also sense predators. So, even if your crabs might not succeed in catching any of your fish, it can still stress them out. Constant stress makes them weak and vulnerable. According to multiple tests, they are likely to suffer from shorter lifespans and might experience additional side effects that could have an overall impact on their health.
Note: Stress effect is not limited to fish and could very well apply universally to dwarf shrimp, freshwater snails, dwarf frogs, and other animals (for example, even dragonfly nymths can feel the predatory fish around!).
Crabs and Their Instinct of Opportunistic Feeders
If you are going to keep crabs as pets, their adult size alone should be enough to understand their temperament, diet, and habitat needs. You don’t want your new crab to eat, or be eaten by another member of your tank, right?
Of course, these creatures are beautiful, but most of them are opportunistic feeders! So, they will eat almost anything that is available in the tank. Therefore, do not be surprised if your crab will truly and actively hunt your fish, shrimp, or snails.
If you think that you can fix this problem by giving them enough food, I would not count on that.
The point is that it is something that they will do on instinct.
I will repeat it once again, even if you give them plenty of food, crabs will still continue to hunt your fish or dwarf shrimp (given a chance).
Crabs in Community Tank. Tips
Nonetheless, if you understand it and are also willing to take risks, there are a few precautions that you might want to take.
Areas to Hide
By keeping varied cover throughout the tank gives them a lot more opportunity to avoid unnecessary attention, especially during molting.
Note: Molting is the process of shedding the old exoskeletons (shells) that limit crab’s growth. All crabs are vulnerable and absolutely helpless during and after molting.
Creating such places in your tank will also allow fish to hide from the predator and find a safe place to spend time.
You can read more about molting in my articles:
- Crabs and Molting Process
- Aquarium: Molting Process and Metabolism of the Dwarf Shrimp
- Do We Need Tank Decoration? Simple Ideas
Avoid Bottom-dweller Fish
Crabs cannot swim. They find food or catch prey on the bottom. Therefore, it is important that you DO NOT keep crabs with bottom dwellers. Otherwise, these fishes will likely become a meal for your crab at some point.
You should give your fish at least a chance to survive. Pick only fast swimming top or mid-dwelling fish.
Tank size
The tank size also matters. It is way easier to catch anything in smaller tanks. A big aquarium will let your fish have more space to roam around and avoid a crab. So, the bigger the tank the better.
Do Your Research!
This is the most important rule. Before getting these cool and strange-looking creatures, you have to understand its requirements and the potential consequences.
Impulse purchases often have a very bad effect. People do not understand that their nature limits options if they want to keep them in a community tank.
Choose small and less aggressive species of crabs.
Crabs and Big Fish
Quite often I see that people believe that the size of the fish can guarantee its safety. Well,
unless it is big enough (or aggressive, like Pufferfish) to eat your crab, this is not always so.
I have already mentioned that crabs can fight back defensively even when there is a bigger enemy in front of them.
Therefore, even fish that are bigger than them, run a pretty significant risk of sustaining damage from an attack. As a result, it can potentially get sick and eventually captured by the crab.
So, don’t be overconfident thinking that your fish are too large or fast for crabs. They can still injure fish enough to kill it at a later time.
In Conclusion
It really does not matter which crab species interests you, or the amount of experience you have in fishkeeping, it is always important to fully research any species before introducing it to your tank.
With a few exceptions, keeping fish, snails, and shrimp with crabs can really be a game of chance. That is why it is not recommended unless you are prepared to potentially lose some fish, snail, shrimp, or other crabs.
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