gravity works, just as long as you have redundancy built it big time.
custom overflow dude. without drilling thats your biggest dance partner.
You can tap off a pump drawing from the display with another in the
sump pumping it back, but i wouldn't go that route unless your clearly commited, to much reliance on pressure or float systems, not to mention the pumps themselves need to be able to handle cold stops & starts if it fluctuates.
