I ended up ordering a dual stage pre-wired controller from them with the heat shrink and just received it. The wiring is really clean and so was the heat shrink.ETC Supply sells heat shrink tubing to protect the Ranco temperature probe from the saltwater environment. It’s very cheap at $1.50/ft and $2 shipping for the tubing. If you order the Ranco controller from them, they will install it for you. They also sell prewired units as well if you’re not into wiring your own controller.
Thermal Well For Aquariums - 3/8" Clear Heat Shrink Tubing
www.etcsupply.com