Auto-topoff for a sump-less tank?

[Richer]

I forgot to mention... this tank is in a tight spot in my basement, I cannot elevate any kind of reservoir over the tank.... so a nurce topoff system or any variants won't work. I need something that will be able to pump water from a reservoir thats on the ground. I saw a Tsunami Topoff system here. Is that any good? Is there anyway I can duplicate this system without spending a hundred bucks?

-Richer