I have a Rio 2500 as my return pump from my fuge and it creates enough current up top, but I have a rio 800 and Rio 180 also in the tank... Question is where is the best place to put the two powerheads? Right now I have the 800 on the left hand side about half way up and the 180 on the opposite right side wall, facing the other, about 3/4 the way up... Should I place them more towards the bottom facing each other? Thanks