It's a good thought to try an active method to combat condensation. Aluminum will self-protect itself, but it needs good contact with air to do so. The only downside to using fans of course, is this becomes an 'extra' thing to do. I'm not sure just blowing air into there will be very effective if there's no where for the damp air to go? But, one fan blowing in and one fan blowing out should work. Still, though, more work than I'd want to do.
Your existing tanks lasted 30 years and they were just plain aluminum? I assume you'll probably have your new tanks epoxy coated, which will make them last much longer. I think I'd just make sure they were properly coated and properly installed (with the underside of the tank 'supports' being very important) and call it day and not hassle with fans. If the tanks now last 40 or 50 years... and no messing with fans every time (which may not add any more life to the tank, anyways)... I'd be a happy camper.