Any dead creature in the water will putrefy and the resultant putrefaction will kill any fish in that water. So yes the dead crab will kill the Betta eventually.
I'm assuming you have access to a fresh water crab because a Betta will not be able to live in salt water. The crab will attempt to catch and eat the slow moving Betta. It is only a matter of time before the Betta is killed.
Maybe, but seeing as how there's so little room, the betta might fight with the crab, or worse! The crab might try to eat your betta! Be careful!
If you put a Crab with a Betta I can almost guarantee the crab will rip chunks out of the Bettas fins first and end up by killing and eating the Betta.
why would you want to kill a betta D:
It's really not a good idea. The crab will start to tear/eat the betta's fins. It may become food for the crab.
no
Betta's are super Territorial once they see another one they go for the kill and one they do their is no stopping it they stop until one is dead even with cory catfish's the will kill anything ( fish) in my book their the king of the world ( and by world i mean tank) so i wouldn't even risk it weather male or female a betta is a betta
yes
it deppends on how big the hermit crabs and the moon crabs are but if the hermit crab is bigger youv'e got your self a dead moon crab
yes betta fish have to live alone or one will kill the other.
Not always, but it's very likely. Some females kill males ;)
LOL. To be honest yes. But it will also kill the betta.