I must be paint happy tonight!
Here's an idea for a sump that does not involve drilling the display or an overflow box.
The sump is fed by a pump in the display (clever hidden behind rocks if possible) and then gravity feeds back into the display. Not for everyone I admit but it serves the function and with only a short height for the water to be pumped up to the sump a small pump like a
Maxi jet 1200 could be used.