Eh.. how come got grease one?... u sure its grease anot.. might be just vaseline or petroleum jelly that the manufacturers apply to the rubber parts to prevent them from drying out. I dont think under water pumps got grease one leh. Any way change like all the water if u scared lor then re rinse the tank again with salt solution just to be safe. See whether you can put the fish on hold first untill u clean your tank up.