A method for controlling bio-slime formation in a water washing tank of an automatic processor, said washing tank having a discharge port at a bottom thereof and at least one transporting roller for passage of photosensitive material through the tank, said washing tank being full of water during an operating period of said processor, said method comprising the steps of:
- discharging the water from said washing tank through said discharge port during a quiescent period of the processor;
- causing said transporting roller to rotate during said quiescent period so as to remove water droplets thereon thereby preventing bio-slime formation during the quiescent period.