A recent study showed that damselfish recognize each other via UV patterns on their faces and bodies. Perhaps some freshwater fish recognize each other in a similar fashion, and the change in light causes them to not recognize a former bully or someone they formerly had a truce with?
Or maybe red light causes them to see something along the lines of submissive markings on other fish, encouraging aggression.
Or maybe red light causes them to see something along the lines of submissive markings on other fish, encouraging aggression.
