10g aquarium

A couple questions here... I am new to this yes, and have been on here and researching and searching the net (although have found more about breeding for feeding purposes and 'keeping you minnows & fry alive' for feeding purposes..yet I am wanting them only as pets..as they are the only...

When is it necessary to put an Air Stone in your aquarium? As I've said I have a 10g aquarium w/ 3 rosy reds atm....I've read alot of ppl have air stones etc. I have a internal corner filter....the water pours from approx 1/2 to 1 in above the water level of the tank. Do I need an air stone?? I...