I need to redue the plumming on my 90 reef and was woundering what size return i should use, and placement. does the return need to be at the top of the tank or should it run down the back wall to the bottom. would this get better water movement ??? right now i have a 3/4 return that goes over the top. just wanted to get some idears befor i go to hd for pipe and fittens thanks ..