I know it's a common issue with magnets and our tanks, so I'm not surprised by this but..still disappointing when it happens to you. I do have the probe holder above the waterline at the moment so hopefully it will be ok in the short term.
I will soon be getting a new tank up and running with a Trigger Triton sump that I think has probe holders built in so maybe I can avoid a magnet holder all together.
But, the fact remains I purchased this probe holder and it didn't even make it a year before rusting. :(