I use this...

https://www.amazon.com/gp/aw/d/B0B31HSKF2?psc=1&ref=ppx_pop_mob_b_asin_title

Wired to this switch...

https://www.amazon.com/Anndason-Pieces-Aquarium-Mounted-Horizontal/dp/B071ZG4Y34/ref=mp_s_a_1_17?crid=39B1TRZBP5S8Q&keywords=water+level+sensor&qid=1688069243&sprefix=water+level+s%2Caps%2C139&sr=8-17

You install so when the switch opens because the water level dropped, the pump engages and fills until the switch closes bc the water level rises enough to do it.