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Are Fiddler Crabs Reef Safe? 

Are Fiddler Crabs Reef Safe

No – fiddler crabs aren’t considered reef safe. While we usually picture crabs in rocks in the wild and would therefore assume that they would do perfectly well in a reef tank, sadly, the two do not really mix. As it happens, there are two main reasons why fiddler crabs will not thrive in a reef tank, and nor will the reef, for that matter! 

First, fiddler crabs need brackish water. Brackish water has a lower salinity level than saltwater, which reef tanks require. Reef tanks are types of saltwater tank and will therefore not be the best environment for fiddler crabs.

While they may survive for a short period, eventually, the environment will become too unsuitable for them, and they could die. Moreover, as you know, fiddler crabs need both water and land in order to thrive. While you could technically have a part of the reef sticking out of the water, it would be best to have a tank that is big enough to provide dry land, as well as plenty of water for the fiddler crab. 

Finally, fiddler crabs, while not aggressive, do also hunt for food. They tend to eat fish that are smaller or of the same size as them. That being the case, it is best not to have them around too many small fish, many of which you are likely to have in your reef tank! Therefore, it would be best to keep your fiddler crabs in a separate, brackish water tank and leave the reef tank to thrive with as many compatible animals as possible. 

Can fiddler crabs live in saltwater? 

You may have noticed fiddler crabs in saltwater tanks in shops or are simply interested in knowing whether they could join one of your saltwater tanks; however, it is essential to know that no, fiddler crabs cannot live for a long time in saltwater tanks. 

As previously mentioned, they are brackish water animals. Brackish water is less salty than saltwater, but has a higher salinity than freshwater. Therefore, it can be difficult to create the perfect balance in a tank – however, it is an essential part of keeping fiddler crabs. 

In order to create the perfect environment for them, you will need to have the most natural freshwater possible. You can either use spring water or, if you have to, water that has been dechlorinated. In a pinch, you can also use tap water – however, it should have been left out for at least an entire day before you put the fiddler crabs in it.

Then, you can add the salt (ensuring that you do not just use table salt!). In order to ensure that you use the perfect amount of salt, you will need to measure the gravity of the water using a hydrometer to ensure that it is between 1.0005 and 1.010. any more or less will not be suitable for the fiddler crabs to live in for a long time. It would be best to frequently measure the gravity of the water to ensure that the salinity level is always at its optimum in order for your fiddler crabs to be able to thrive. 

Can you put fiddler crabs in with fish? 

Fish aren’t ideal for housing with fiddler crabs, as said crabs can and will attack them. As you may know, fiddler crabs are, generally, relatively calm animals that can do very well in tanks. However, it can be a little difficult to find the perfect animals to pair with them alongside.

Fiddler crabs can happily live on a diet of shredded shrimp, flake fish food, and even dried cat food. However, if they are confronted with fresh fish in their homes, then they will naturally aim to eat them! Fiddler crabs often only attack fish that are either smaller or of the same size as them. However, if they are being attacked by the fish, no matter the size, then they will defend themselves, potentially harming or killing the fish. 

Moreover, since fiddler crabs are brackish water creatures, as well as amphibious, they need a very particular kind of tank. They need plenty of land, as well as requisite water. In order to keep them with any species of fish, you will need to ensure that the fish can live in the same kind of water as the fiddler crabs and that the fish have enough water to be able to move about and not feel threatened by the lack of space.

You would therefore need a very big tank. That being said, it is not unheard of to house fiddler crabs with fish. However, it is essential to understand that it is a bit of a gamble. Whether they can thrive together also depends on the temperament of the particular animals. 

Will crabs eat my coral? 

There are indeed plenty of crabs that will eat coral, and algae, fish, and all parts of a reef! That is why choosing the right crabs for your reef tank is essential. Fiddler crabs are not ideal for reef tanks, as they simply cannot provide the best environment. That being said, there are plenty of crabs that can live in a reef tank, and that can actually help it to thrive. 

Reef safe crabs are actually an essential part of any thriving reef tank. This is because the crabs help to maintain the algae debris and can even help to maintain a cyanobacteria bloom. However, getting the wrong types of crabs can lead to dead fish, destroyed corals, and other issues in the tank. 

With that in mind, here are some of the best crabs that you can add to your reef tank:

  • Blue leg hermit crab
  • Red leg Cortez hermit crab
  • Red leg hermit crab
  • Orange leg hermit crab
  • Electric blue crab
  • Emerald crab
  • Blue eye hermit crab
  • Strawberry crab
  • Zebra reef hermit crab
  • Arrow crab
  • Boxing crab
  • Anemone crab
  • Horseshoe crab
  • Trapezia Pocillopora / Acropora crab
  • Sally lightfoot crab

As you can see, you are spoiled for choice when it comes to crabs that you can safely introduce into a coral reef environment. Just be aware that, yes, these crabs will occasionally take a nibble or two – so please don’t be too surprised if your reef starts disappearing!

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