I have two bettas. Both are healthy and active, but one of them snaps at my finger even when there is no food. The other one just stares at it and waits for food. Does this show their level of aggression or something? Also, why do they always open and close their mouths quickly and frequently when they have the labyrinth organ? Is it from excitement?

Thanks!

Well Betta's are just like people, everyone of them has a different personality. Some are pretty docile, some are super agressive, and there are those who are inbetween. I would guess that your little finger nipper would fall under the more aggressive catagory, while the other guy who just waits for his food is probably just a little bit calmer Betta. pets question and answers,www.5d2d.com
As far as the mouth opening and closing, it sounds pretty normal to me. Just because a Betta can breath air from the atmosphere like we do, doesn't mean that he won't absorb oxygen through his gills like any other fish.

Well hope that helps!

The one that snaps your finger is just more brave than the other.The opening and closing of the mouth is probably a sign of aggression.If this is two males in the same tank,one will more than likely kill the other.

male and female
male and male
or
female and female
cause it could be anything