Want to build a optical high water sensor

[Johnic]

I have an auto water changing system in my setup and I want to have an optical water level sensor mounted about 1/4" higher than the designated sump height just in case the water changer adds slightly too much water it will kick on and drive a very small pump to remove the excess. I want to have this in place as not to add too much salt water and drive up the salinity and to have a safety system in place.

Any thoughts on how to do this. I was going to but the Tunze Nano ATO and just turn the float upside down so it will kick on when water is to high but I was thinking to use an optical sensor instead for more reliability and accuracy.

Any thoughts ?

PS: I dont have a controller...