Wow, that helps out ALOT ..... cschweitzer, it has to be like, well, a simple paper, for my teacher to understand, i will like talk about one thing each paragragh, like in one paragragh i would talk about Rock and sand displacement, and the next talk about the salinity of the water, and so on and so forth, i sadly live too far away form SITC to go there daily, even weekly... and in my tank, i have not had the need to focus on "flow" really, so i dont know all abotu that suff, but apparelty YOU do, could you tell me some basics, and i can expound on them to create a paragragh about it. Thanks for all the help so far guys, i appreciate it