Benneficial bacteria is somewhat of a mystery to me. The only thing i realy know about it is that when a system has a good colonization of it then plants get fed and fish get cleaner water. I know that with an established bacteria amonia gets turned into nitrite and nitrite into nitrate and all is good.      The project:  I'm building a 50 gallon AP system. 25 G. in the tank and 25 G. in t…