Why is My Fiddler Crab Upside-Down? (4 Possible Reasons)

Fiddler Crab Upside-down

I have read many questions from aquarium keepers about their fiddler crabs staying upside down in their tanks. If you’re reading this article, it means you must have had the same experience with them, and decided to know why your fiddler crab is behaving that way. You will agree with me that, crabs staying upside down is not normal at all, so there are some causes for that. So In this article, we will be learning some common reasons why your fiddler crab may be staying upside down in its tank.

Why is my fiddler crab upside down? Your fiddler crab might be upside down because it is about to Molt, it is dying or the water is too cold for it.

Fiddler Crab Upside-down

The fact is, fiddler crabs staying in that position is not cool and will break your heart when it does that.

So the above are some common reasons they do that, we will look further to some other reasons in this article.

Fiddler crabs staying upside down is not normal, and they can hardly do it unless there is a problem.

Just know that something is wrong with your crab when it stays upside down, and try to find out why.

Related: Why is my Crab-eating sand?

common reasons why fiddler crabs can stay upside down

Some of the reasons why fiddler crabs can stay upside down are:

When they are cold: You might be surprised, but yes, crabs and other crustaceans do get cold.

Related: Is my Fiddler Crab dead or Molting?

Every animal has its normal temperature that its body is adapted to and once the temperature exceeds or is below, then the animal will not be totally okay, and so might start acting strange.

In the case of fiddler crabs staying upside down and twitching their legs, it might be a sign of cold.

So you might need to check the water temperature and provide them with a heater if possible.

Related: 5 reasons why your Crayfish is floating

The normal water temperature for many crabs, which fiddler crabs fall into is 75 -84°F.

So if the temperature goes beyond this, the crabs will get cold and that might be the reason your fiddler crab is upside down with its legs twitching.

When they’re about to Molt:

Molting is a normal thing for all crustaceans, and they must do this in order to grow, sometimes fiddler crabs and other crabs will prefer to stay upside down during this period or immediately after.

Although this rarely happens, but in some cases, it does happen.

If your fiddler is upside down, you might want to check if it is about to Molt by observing the body for any sign of peeling or breakage.

If there is, then don’t touch it, leave it to Molt successfully because trying to bring him back upright might cause some damage to it.

If molting is why your fiddler crab is upside down, then you don’t need to do anything, just provide calcium for it and leave it in peace to Molt successfully.

When the water is not suitable for them:

Fiddler crabs staying upside down happens a lot when the water they’re in is not suitable for them.

For instance, when the water parameters and the type of water they need are not there for them.

Fiddler crabs are salt or brackish water dwellers and do not survive for long in freshwater.

So the type of water they’re into matters a lot. Or maybe the amount of salt in the water is not significant enough to suit their body.

Again they are easily stressed.
So leaving them all in water without providing them with a way to get to the surface and breathe air could stress them and might lead to them staying upside down.

When they are Dying or Dead:

This is the hardest word any pet keeper would want to hear.

Well, am sorry to say the word to you.

The fact is, when crustaceans die or are dying, some of them normally stay upside down till they’re removed from the tank.

The case of your fiddler crab staying upside down, especially when it is motionless is probably because it is dead!.

To know if your crab is dead when it is upside down, it will stop twitching its legs and will not show any sign of movement even if you stroke it.

So remove it from the tank when this happens.


These are some of the common reasons your fiddler crab maybe be upside down.

Like I always say, am not a doctor. So consult the advice of a vet whenever your pet’s behavior gets complicated.