New to Arrow Crabs.

[Tinnerito]

I'm thinking about adding an arrow crab to one of my aquariums. I've done all of the general care research on the internet, but some information I have been unable to get a hold of, so I came here to get some info from any invert or crab experts out there.

I read that arrow crabs are territorial, but about how much space do they usually occupy?

Would an arrow crab attack any creature that enters its territory? Or only some individuals maybe?

How compatible are arrow crabs with macroalgae, snails, hermits, and shrimp?

I hear about many arrow crabs being friendly towards fish after being in a quarantine box, but would this still apply to the small 1-3 inch gobies?

How sensitive are they regarding water parameters?

Any answers help. Happy reefing!

 

[vaguelyreeflike]

Arrow crabs can successfully be housed with mature male and female pairs in tanks larger than 50gals, but there is always the chance the female may get sick of the males advances and kill him. I’ve had females fatally injure males within 30seconds by pinching at their mouth parts in a way that leaves them unable to eat, molt or breathe properly. Have also had females break the rostrum and claws/legs of males very quickly too, thats a survivable injury though. Two males will almost always compete and two females seems to be 50/50. they are sexually mature at around 4-6” total length but sexable at a very young age like most true crabs by looking at the shape and size of the abdominal flap.

They dont hurt hermit crabs, other species of crabs (true or false), snails, shrimp or coral in my experience (although I live by the saying “never trust a crab” as any can become a problem towards the above), they will try to grab small fish, however they’re not very skilled at catching them. The risk will always be there for your fish, if one gets sick or injured they will be fair game as they are opportunistic hunters and scavengers.

I’ve cared for probably around 30+ over the last 3ish years, I order 3-4 every other month but have never had an adult in my care, theyve all ranged from 4-6” (this includes legs). ive read and heard that behaviour around fish changes once theyre fully grown at 9-10” across where they become more likely to hunt. Females will generally be smaller than males as adults.

This has just been my experience with them, im sure others have had other success/failure stories for you.

 

[Tinnerito]

Arrow crabs can successfully be housed with mature male and female pairs in tanks larger than 50gals, but there is always the chance the female may get sick of the males advances and kill him. I’ve had females fatally injure males within 30seconds by pinching at their mouth parts in a way that leaves them unable to eat, molt or breathe properly. Have also had females break the rostrum and claws/legs of males very quickly too, thats a survivable injury though. Two males will almost always compete and two females seems to be 50/50. they are sexually mature at around 4-6” total length but sexable at a very young age like most true crabs by looking at the shape and size of the abdominal flap.

They dont hurt hermit crabs, other species of crabs (true or false), snails, shrimp or coral in my experience (although I live by the saying “never trust a crab” as any can become a problem towards the above), they will try to grab small fish, however they’re not very skilled at catching them. The risk will always be there for your fish, if one gets sick or injured they will be fair game as they are opportunistic hunters and scavengers.

I’ve cared for probably around 30+ over the last 3ish years, I order 3-4 every other month but have never had an adult in my care, theyve all ranged from 4-6” (this includes legs). ive read and heard that behaviour around fish changes once theyre fully grown at 9-10” across where they become more likely to hunt. Females will generally be smaller than males as adults.

This has just been my experience with them, im sure others have had other success/failure stories for you.

I appreciate the information!

 

[vaguelyreeflike]

How sensitive are they regarding water parameters?

they seem to be fairly forgiving with parameters, I lost a few to a dramatic salinity/alkalinity drop that I didn’t catch for over a week (my fault completely), but other than that the only losses I’ve had were from arrow on arrow violence lol. Like all invertebrates they appreciate an occasional iodine dose in the tank. In a 100gal system I add a single drop once every 2-3 weeks, but have heard of people dosing daily. Its worth it to test for iodine although most iodine tests are fairly inaccurate so can be difficult. Any sign of molting issues and it should be dosed. They also seem to handle temperature swings very well in my experience.

 

[vaguelyreeflike]

I appreciate the information!

No worries!