It sounds like you did not initially establish a bromide bank by adding 1/2 ounce per 100 gallons initially. If you did, then a properly functioning ozonator would be producing more bromine from the bromide bank -- probably enough to maintain a bromine level when not soaking, but you would still likely need to add an oxidizer (usually chlorine or non-chlorine shock, MPS) after each soak unless you soak infrequently and for a short time.