You will not be successful trying to "suck" this stuff out. Suction velocities are of necessity low.

Drain the tank and then jet it out via the drain, or better still, get inside the tank and clean it properly.

Why do you want the water to arrive to the tank?

In our normal lubrication systems (of course for oil), we provide a return oil filter for capturing these along with magnetic inserts for the feroomagnetic debris.

In your case also you may try using this.

In addition you may allow the water to settle down in a cleaning box (reducing the flow) and allowing the heavy particle to settle down and then strained. filtered.

making it to pass through the pump means you are damaging the moving parts of the pump, whether it is PD (screw/ gear) or centrifugal.

Additionally the tank outlet should not be at bottom, but just a bit higher so that the sediments are not sucked out.