Lost a bank in the sump need to glue a new bank in silicone is going to take to long to dry. And tank has fish and corals. Was thinking to use epoxy or a glue that fry's fast and wont affect the fish
As long as you can provide good water circulation and bring the heater(s) from the sump into your display tank so the temperature is kept in check, taking your sump offline for a day or two should not have any deleterious effects on your fish/corals.
Place the heaters + some powerheads in the display tank. Turn off waterflow to sump, drain sump, silicone in new baffle. Allow to cure for 24-48 hours (use GE 1 silicone), mix up new saltwater and then put sump back online.