Such big pupils yours have, mine have very tiny pupils. It may be my lights are just too bright, I need to get some big leaf plants to create shade. Can you show the backs of yours in brighter light they look like they might be non-standard purples which is of course way cool! Here is the panzerwelten Geosesarma crab photo galleries helpful to try and find out what you have:
http://www.panzerwelten.de/v/Geosesarma/
My guess from your pics is that you actually have the Geosesarma sp. "blue" and not the standard vampire crab (G. biciolor) since it doesn't look like yours have an orange or yellow blotch on their backs.
Here's one of my reds plotting his next move:
Hopefully you will get babies. I'm checking all the time to see if I can find babies or "jelly bellies" (egg sack) on the females. Supposedly the litters are as high as 40 "pups" most of who will survive if pulled out of the communal enclosure and raised individually to ensure adequate feeding and non-aggression from tank mates. My red species supposedly do not carry their young around on their backs like the purples and orange do. If you see yours with a "baby wig" just capture the mother and put her in a nearly empty tank until she releases the young. Babies of mine will simply have to be discovered by sheer dumb luck! LOL
Have you found some good online forums for the Vampire Crabs (Geosesarma sp.)? I have only found these two:
http://www.junglebox.co.uk
&
http://www.panzerwelten.de
You have to type the Panzerwelten URL into google and read it via translation unless you read German. It's kind of weird reading translated posts but you get the drift of what people are saying, sometimes it just makes you laugh though with the word substitutions. But the Germans have been keeping these longer than Americans so they have some good reading material there. You can make a post in English and Oliver (site admin) will answer you as well as those who read English will often help. Both are good forums, but the main thing is these crabs are so new people really don't know a lot about them. Seems each color form / species has different habits. There are estimated about 90 different Geosesarma species in SE Asia only a few of which are available and even fewer of which are even scientifically described and officially named. Mine are known only as "Geosesarma sp. "Red""
What are you feeding yours? Mine get a rotation of the following:
Live & dead crickets
Isopods / Sow Bugs / Rolly Pollies / Pill Bugs
Dead Blue Bottle Flies
freeze dried Gemmarus shrimp rehydrated in water
defrosted mysis shrimp
Tropical fish flakes
I've seen them carrying dried oak leaf litter around and into their burrows so they may be padding their burrows or eating it, they often take their food into their burrow and eat so who knows what's going on in there. Autopsies on wild crabs found that 77% of their gut content was the substrate they were living on.
I've tried non-citrus fruits but so far they don't want strawberries or cherries