It's convenient to buy float switches,and you find them in most electroric supply stores.
You have two choices of float switches: vertical and horizontal. Vertical float switches consist of a tube with a floating ring, while horizontal float switches have a single bar-like piece with a hinge that opens or closes based on the water level. In both types, you mount them so the switch is open when the aquarium is too low when using them in a top-off system.
Main Products:Pressure Switch,Pressure Control Switch,Cable Float Switch,Float Switch.