I want to get two sensors for my tanks and not cut more holes in them. the top of of gray water tank is inaccessible. the nomadic control helix says it is not compatible.
Mopeka is your best bet.
SeeLevel with CANbus integration, Fathom Radar, Mopeka are all known to work with the Cerbo. I haven’t tried the Fathom Radar sensors but I have some on order. If you can’t get to the top, then I think the SeeLevel sensors might be your best bet.
With a little integration work, anything that has an API and local access can be configured to work with the cerbo, especially now with nodered and virtual devices.
I saw a nice affordable Chinese top-down sensor this week, it was powered by Tuya so would work well.
I have my heatpump, smart switches etc all integrated that use the same spec.
I had never heard of Tuya before. Thanks for giving me another rat hole to explore in my “free” time. 
thank you all. I like the Mopeka. Except I have one water tank sitting on the floor and I have to keep access to change the battery. but I think I can handle that by emptying the tank when it goes dead.