Sink-float tanks for plastic scraps separation

Yes, a tank is a tank so what's the deal with it ?
Most of everybody, mainly "beginners" did their own construction simply because everybody is in position to put together a tank.
Talking about a tank that will handle, as main material, a floating one, what everybody find out is this tank does not separate as much as it was supposed to, just because all parameters should be taken into consideration and they wasn't.
These parameters are:
The ratio between the surface area of the tank and the volume of flakes in the unit time.
The apparent volume of flakes (when dry)
The density of each material (the good one and contaminants)
The speed of the water on the surface of the tank.
The capacity of dewatering system at the end of the tank
The way the flakes are fed into the tank (on the surface or under it)
The turbulence of water under the surface
The angle of the sides connecting to the bottom
How clean the water inside the tank is

And this as far as technology.
When it goes to motor-reducers set up, screw conveyors dimension and speed, size of screens, pumps dimension and impellers shape, valves, level control etc. what it comes up is normally something messed up.
Not to mention if rolls with sprockets and chains are mounted to make it "better performing"
So, it is true that a tank is only a tank, but a trouble-free, efficient one, is another kind of device.
Rings the bell ?