If you want to increase the flow rate to entrain turds and carry them to your mechanical filter, then you will need larger diameter gravel. The velocities needed to pick up the stuff shown in your picture will blow your sand around as well.
You can use a white quartz gravel and mix it in with your sand in order to give it some stability if you want to add flowrate.
You can use a white quartz gravel and mix it in with your sand in order to give it some stability if you want to add flowrate.