Some time ago we all agreed that in a planted tank it's better to have laminar flow. Compared to turbulent flow it should provide better removal of the particles that we want to go through the filter.
We talked about ADA's way of setting up the outflow and inflow. How they make a gyre - a directed stream of water that "pulls" particles from all parts of the tank.
We all agreed that perfect laminar flow is impossible to create in a planted tank. But one needs to strive to be as close as possible.
Well, this video will give you a very good visual idea how the water in the aquarium can be seen as a single body. That's the basic idea behind using a gyre and the efforts to maintain laminar flow. Simply put if we can grab and pull the water in one corner of the tank we can move the entire volume of water. And make it go through the filter. And all the particles, from all corners of the tank too of course...
Hope that makes sense. And hope that the people that were interested in that discussion still remember it. Here, this is how the water can be seen behaving as a whole body. The effect is created by using a special pump set to work in a special mode. Simply put it's like pushing a swing - a small push in the right moment and place makes the entire swing go back and forth further and further and further. Meaning that if you pull gently at one "end" of the water and keep doing it you will involve the entire body of water and if the debries from around the entire tank are in suspension they will come along too: http://www.youtube.com/watch?v=AB5dfLYkK7k