Tiny micro bubbles coming from returns

[krdowns]

Since we started using our pool this season, I have noticed tiny little bubbles coming from the returns. I'm not sure if we have an air leak somewhere in a suction line or if this might be caused by the swcg. I've also noticed that the basket on the pump is not full and the pump wants to re-prime itself sometimes. This makes me think that there's air coming in somewhere. Any ideas? I am going to test the water tomorrow, so I don't have any figures on levels right now.

Edit: I have a 4 speed pump, which is normally running on the #2 setting. When it's running #3, the bubbles don't seem to be there and the basket on the pump is full.