The only thing that I have found that cleans tank sensors is bleach. Fill the tank(s) to about 1/4'ish, add one full gallon of bleach and drive a couple of hundred miles. Works great on smelly gray tanks that have kitchen sink residue in them. With this being said, I really could care less about my black tank sensors. When the tank burps when flushing it is full and time to dump.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof