Thinking of mounting my r4 to the back wall of my aio and that would put the magnet in the rear sump(filter chamber or whatever it is called in a aio)
Is the magnet safe there or will it break down?
I personally wouldn't do it, though I'm sure there is some who have with little consequences. You could coat it in an epoxy or even just put it in a fish bag and just double it up to be safe since it will be hidden in the back and out of site.