Emerald Crab Problems

[ArowanaLover1902]

I've been having problems with these crabs since I started the hobby, I've gone through 3 and am fixing to give yet another to the LFS. I keep buying females, I'm told these are the ones that are the big algae eaters and are responsible for the algae consuming name the mithrax genus posseses. Every time I get one it'll eat any and all algae for a month or so, then it hides for about 2 weeks (a bit of variation on this number, but this is the average for me) and finally returns as a giant crab, having literally doubled to tripled in size and now possessing the large claws characteristic of a male. Are they changing gender, was it ever a girl in the first place? My current one (who has grown faster than the others by far) is big enough to actually hurt if he pinched me and hasn't messed with any of the corals or livestock yet, but could probably eat my barnacle blenny if he wanted to (he may have eaten the other two that I haven't seen for a bit). If I bought more than one would competition prevent this change?

 

[Kali]

Crabs don't change sex. You can tell the difference by looking at the underside of the crab. Males have a narrow "flap" and Females have a wider one.

Scroll to the bottom of this link and it'll show you the difference between them: http://dlnr.hawaii.gov/dar/fishing/...-to-determine-sex-of-regulated-invertebrates/

 

[ArowanaLover1902]

Thanks, I guess my crabs just get really big, well I guess I'll just replace them every month or so, they're only about $5 from the LFS.