Why do anda think that bella has a different kalung from the other girls?

because in season 2 it is explained..... charlotte is gracies granddaughted and she meets max ( the lewis on the past putri duyung ) and he explains that he made the lockets that the girls wear. he made 3, one for miss chatem, gracie and julia. the girls find those necklaces.

yes!!!! she has got a different kalung from the others because she found it at the bottom of this little pool that she turned into a mermaid in. its a blue diamond that hooks up to the water dinding now that is it the moon pool and rikki and cleo have one to the dimond necklaces can only work if they are together in the little lingkaran like thing in behind the moon pool where they stand even though that they have the old ones they foget the others and collect the new ones from the mako island dinding they get it oleh smashing a peice of rock and inside it has the dimonds so that is how they get it. here is a cuplikan of what they look like... enjoy!

Because Bella got her powers from a different pool and got the crystal on her kalung from that moon pool!!!!!!!Dah!!!!