Hi, my name is George Bouris.
Yes, you can replace the existing sensors, with sensors similar to what you suggest.
Considering that the input to your PCB is a common input with pull-up resistor, a very small and simple circuit required to connect this type of sensors. It may have the form of an adaptor with one male and one female connectors, so it will seamlessly connect to the existing PCB.
However, this type of sensors performs electrolysis (current flows through the water), which has two consequences:
- It slightly affects the water.
- The sensor's electrodes oxidise relatively soon
I wasn't able to find ready made such sensors and these that you suggest will be oxidised soon (their electrodes are very thin). You need something that will last for a few years at least, I guess, so you probably need to build something custom. In my opinion you should use some kind of stainless steel.
If you're interested, I can build such a custom sensor and its interface PCB.