[jostafew]

Best thing I came up with is marine grade paint. It smells pretty strong while it's curing, but it's the kind of stuff they use outdoors in wet situations. Once that's on there, no more worries about spilled water! I'd bet that if you simply remove as much of the surface mould as you can and dry the area well, simply putting a couple coats of that marine paint over top would seal it all in. Once that's done it's a matter of fixing the source of the problem by ensuring that the cabinet is be well ventilated. If you're worried about evaporation, build a lid for the sump. Might be overkill but my sump is completely covered (DT is open top though) and the cabinet is ventilated by a fan 24/7. I want to make sure that my electrics aren't damaged by moist salty air.