Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Psilocybin is the psychoactive compound that puts the “magic” in magic mushrooms. Ingest enough of a fungus like Psilocybe cubensis, and users are liable to experience sensory hallucinations, euphoria, and even altered perceptions of time. Mounting research also suggests that smaller, microdosed amounts may offer promising alternative therapeutic options for treating PTSD, depression, and even alcoholism. But what happens when you give fish the same psychoactive ingredient? It may sound like an odd, even pointless experiment, but biological neuroscientists think the results could inform future medical and psychiatric treatments. Their evidence laid out in a study published today in the journal Frontiers in Behavioral Neuroscience suggests small levels of psilocybin ease anxiety or aggression. Or, at the very least, it calms down a notoriously mean species of fish. The mean fish in question is the mangrove rivulus (Kryptolebias marmoratus). It is a remarkable creature found along the coast of Florida all the way to Brazil.The 1.5 to three inch …