"Advisable to put a tank near to a electrical product?"
Well from my experience, I don't have much of a problem with rusting, its just the occasional splash of water, so its best in both favors to protect the electrical product from any water contact or put it somewhere that is safe from it. Protecting also may be something like covering it up.
Throughout the years I've never really had any rust problems, however, parts inside the product or whatever you're afraid of might not be rust resistant. Also, too much humidity will eventually wear it out weither it is water proof or not. My plugs and anything that I know that might get damaged by water is placed at least 2ft or so away from it. I don't know, this is all in my experience.
What do
I know
Hope I help a little if not a bit more.