For the tanks just buy a 6’ cable and wrap it around the tank base, feed it through the loop at one end, then feed it up and through the tops of the tanks. Then just lock the other loop to the cable with a padlock.
I have one on our tanks from when we stored the 32 at a relatives. More so for the just in case scenerio since it was not an area of concern normally. Figure why take it off.
I also have a cable locking the spare tire as well for the same reason.
Something like this:
6’ cable lock
Either the 1/4” or 3/8”, up to you. Buy two cables and a 3 (or 4) pack of keyed alike locks. That way you’re all set with matching keys. Put a key on each tt key set, hang one in the tt as an extra, and possibly one in the tv for “safe keeping”! Lol