Cutting off the return pump

[Guppies Onli]

I intend to add a sump below my stand to my 2ft tank. But as the main tank does not have any internal hole drilled for the overflow, I'll be using those overflow durso pipe and a return pump.

My main concern is when the overflow pipe break siphon due to trapped air bubbles in the long run, the return pump will keep pumping water in the last chamber until dry. This may overheat the pump.

So is the onli way is to monitor the water level in the last chamber of the sump where the return pump is, with a float switch.

May I know how to connect this float switch to cut off the return pump? Is a level controller needed in this case (which is very expensive $200+ right)? Or is juz a float switch connect to a relay; but how to?

Thanks for helping out.