Check these little guys out.. You Drill an empty / half / full level hole in your tank and then wire these little sensors to your monitor. Very easy to install. https://www.amazon.ca/KIB-MP5-Screw-...sr=1-9-catcorr
these guys have most of the options, I like the non invasive probes, haven't had one fail in over 10 years of use https://tankedge.com/techsupport.html