In this Naked Scientists Question and Answer show, we find out if bacteria will grow on a bar of soap, why bird poo is white and whether or not a moon can have its own moon. Also, do sweeteners alter your metabolism and can we re-stock the oceans with farmed fish? Plus, we explore the oily threat to Bluefin Tuna, a newly discovered way that blood vessels in the brain clear a blockage, how channels on Mars reveal secrets about the Martian climate, and why shape is essential for H. plyori - a gut bug associated with ulcers and cancer. In Kitchen Science, Ben and Dave recreate a classic experiment to show that flames are hollow!