I hate to revive this thread, but has no one actually
read the page that
@juntjoo linked to earlier that advertises this contraption for sale at Wally-World? Further down the page (use the scroll key) there is a link to the
Aqua Cube Fountian Operating Guide. The "Guide" clearly shows that the pump is powered from a wall-wart, and that it can be disconnected from same by means of a barrel connector for purposes of cleaning it. In other words the pump uses a small PMDC motor, probably operating at 12 V DC or less. The OP could break one of the pair of wires on either side of the barrel connector to insert normally-open contacts of a micro-switch, or whatever other contraption is desired, without worrying about coming in contact with mains voltages.
We have been owned by several cats over the years: some indoor, some outdoor, and one of them a feral kitten (rescued by wife from inside a cinder block) who decided she mainly preferred indoor life. Not once have we ever thought that anything more complicated than a bowl of water plus a bowl of dry cat food, placed on the floor in the kitchen, was necessary for their well being.