I think along the same lines dman. I'm always curious about the strange life forms that might take up residence. As with most things, there are up sides and down sides to everything. I think a long cycling session will reveal unwanted critters. Apparently, there is the possibility of algae spores that can sprout when the right conditions are met (light, ect.), so you may want to expose to light while you are at it to see what shows up. If you don't like what you see, just put it through some sterilization method.