In many cases, mucus emission is a sign of stress and NOT feeding response. The type of stress can be too much current/flow, biofouling, pathogens, UV radiation, sedimentation, pollutants, desiccation and even temperature or salinity changes. In Most cases, its a defense mechanism against desiccation. Corals coat their body with mucus, keeping in moisture to withstand severe environmental conditions and changes in conditions. Corals in general has mucus which contains substances called mycosporine-like amino acids that can absorb UV light, which can protect corals from strong UV light. When sediments such as silt and sand fall down onto their coral surface, they use mucus to clean up their surface.
So some stated, they see this after feeding. The reason is, they use mucus as a tool to capture prey items such as bacteria and small zooplankton with their sticky surface. Corals transport the food items trapped by mucus into their mouth using ciliary movements and also release mucus as excretory pathways for excess organic matter .
The mucus can be slimy, stringy, in sheets and web-like
