Hi..I would use 2 simple submersible float switches, one at the top of the tank, one half way down (at min level). When the top contacts water inlet off, when the top and bottom has no contact water on.
You should consider a 240v relay and attach a washing machine inlet valve to control the water.
I would also install an overflow pipe into the tank just to be on the safe side, you don’t want to come home and see your fish looking at you from front room window.