oh you can over water RW just about like everything else. RW holds water very well, in fact now that I dont use it anymore (clone in Rapid Rooter and right into Hydrotron) I have had zero algae when plants were small and creating no shade at base. RW also has a bad habit of holding salts very well too so Plain Ph'd water flushes every couple weeks wont hurt or you can spend more cash and buy some Clearex and do same thing.

and yes the tub thing that floods is E&F ( Ebb and Flow for those taking notes ......... there will be a test!!)