When is it a good time to start giving your baby Gerber Food 3rd stage?

My baby is about 7 months old. As of now, he takes the 2nd stage foods. The thing is he takes 3 of those little containers for a whole meal. I was just wondering...should I start giving him the 3rd stage? Are the 3rd stage foods a little different in consistency then the 2nd stage foods? or should I wait til he gets 8 months? Thanks for your help.