i had the power head that someone posted the link to on here. it was on my 90 gal and was WAY too much for my 90... the oscar looked like a pickup truck in a midwestern tornado.
the power head and water dynamics are interesting to say the least.
i have a small power head now on the left side of the tank towards the top of the tank pointing to the right side. the current goes across the top, hits the wall, and goes down to towards the bottom of the tank. this carries sediment across the bottom of the tank to the filter inlet.
when i had it pointing towards the bottom across the tank at 45 degree, it barely moved anything. even when i had it near the bottom, it didnt move as much sediment.
i think its easier to move water near the surface than it is to move water near the bottom.