Kodak gives very sensible instructions for small tank processing on their web site. It involves intermittent agitation that avoids bubbles in the developer. But, all water has dissolved air in it. And, bubbles arise from water exiting the tap into your sink. Watch for it on film when you wash the film. Tiny bubbles there with no agitation. The idea is to break up those bubbles by using agitation. At least that is one purpose of agitation.