I recently brewed my second batch and went with a porter(my first was an IPA and turned out wonderful). Currently it is in the fermentation stage and I'm a little concerned with the yeast I used. When I made my first batch (IPA), after sealing up the fermenter, the airlock started bubbling vigorously right away. With the porter batch this did not happen, It took about six hours to get constant bubbling out of the airlock after sealing. The constant bubbling went for about a day and then slowed down again. I am not the impatient type and I realized it would take four to six months for a typical porter to be ready but I did expect a little more activity in the beginning. Does anyone have any advice for me? Should I add more yeast?