Here is a way to check the circulation:
start with a stick that is long enough to reach the bottom of the tank.
Tie bits of thread to the stick every few inches.
Start your pumps and put the stick in the tank in many places. See how the thread moves.
If you get a consistent pattern with the thread that shows a good pattern of circulation you are on the right track.
If the threads are going every which way, or hanging, limp, then the pumps are creating turbulence or cancelling each other out. This is bad.
Another way to check this is to put something like fish food in the water and watch it sink. This is harder to figure out, though easier to do. You may have to add a lot of fish food before you start to see a pattern, and to see what the circulation is doing all over the tank.
Here is how I would start in on this problem:
1) Set up the filter as the main source of water movement. The water should sheet across the surface, hit the glass (usually at the front, but not always) then move to the bottom. As it moves across the bottom it should move the debris toward the filter intake.
2) Add power heads to increase the water movement in dead areas, to get the debris moving so it can be picked up by the filter.