Most people don't realise that the rather innocuous activity of fish feeding can have severe implications for the health of coral reefs. Repeated tours to feed fish at the same location can lead to a behaviour called conditioning, where the animal learns to associate humans with food. This is great for the tour operator as they are guaranteed plenty of fish for their customers to feed, and the customers are happy as they can interact closely with lots of different fishes. Studies have shown that fish that have been hand-fed over a long period of time are less competitive than those that have not. By providing a supplementary food source through hand-feeding, fish may become satiated quickly, leading to a reduction in the amount of algal grazing. Over time in areas where hand-feeding regularly occurs, an increase in algal growth will outcompete corals leading to a possible phase shift in the reef environment.