Gill recommend 7010 Liquid Level Sensor for all new installations:
The 1612 Stainless Steel Liquid Level Sensor is the stainless-steel version of the 1612 Lightweight Liquid Level Sensor, designed specifically for aggressive or corrosive liquids including salt water, coolant, acids and chemical-based liquids.
The sensor features an SAE 5-bolt mounting pattern and is manufactured to your custom length requirement up to 1.5 meters.