ok so i went to go check out the petstore to buy food and see what new things they have gotten in and saw these really cool crabs that had bright red carapaces. the lady said they also had ones that were purple as well but i didnt see these, they also had fiddler crabs in another tank. i have been looking for something cool to put in my empty 20g long and thought these might be the perfect addition. i know the fiddlers would need land and if the other crabs are indeed vampires then they would need land as well but is there anything else that these crabs could be? and i have never had any crabs like this so any other advice on care would be great. right now i have the tank set up as a full aquarium but would have no issue with draining it and pushing over the sand to create some land for them. also can all these different crabs be kept together or would they fight? and how many could i comfortably keep in a 30in long tank with about half of it as land or more if needed (how much water should they have?)