You have three options: Gravity feed (place water above tank and control flow with a solenoid), siphon feed (container at same level as water line), or pump feed.
I think gravity feed is your only option for that much top off.
Physics are against you on pump feed, so you'll need some way of lifting liquid. Traditionally we would use a peristaltic pump, but you are trying to avoid that.
The only other method I know if and have used is pressure driven. This works ok for small tanks, but I don't think it will scale to your size. The concept is to use a large container (gallon Apple juice container in my case), an air powered airstone is used to create pressure, and that forces water through a second tube into the tank. I used airline tubing through the cap and a smart outlet to make it run for 4 minutes (what I needed for my use).
I used this to top off a Spec V at work while I was out for over a month, and it worked well. Do some trial runs to measure volume, run time needed, and test.