That won't hurt it a bit. Longer, and it will heat up, doing damage to bushings/bearings/motor. If you keep the time minimal, you'll have no problems.
Dan
The only way to remove nitrates within the tank is to have anaerobic live sand or really big live rock. This just about requires 4-6" of substrate.You probably do not want to fill your display with that much, so put a sump/pump/skimmer setup in, and partition the sump off to house the dsb in one...
