Best top off system?

[ponokareefer]

I've got 2 tunze top off's. Lately, my power connector that plugs into the controller doesn't always connect. I looked inside and see there is a build up of salt/corrosion. Has anyone had this issue with Tunze and fixed it? I'm worried one day it won't power-up and stop filling up my tank. I'm not sure what to use to clean it up and how to actually get to it to clean it up.