I've had hornwort and ambulia as floating plants but they don't seem to kill each other off. Based on my experience, I think hornwort allelopathy only seem to affect certain types of algae.imyourhuckleberry said:I read that Hornwort releases a chemical that kills other plants around it. Has anyone experienced this? I have basic lighting and no co2. So far I’ve only picked plants that can grow easily in my gravel without soil. Was adding hornwort a bad idea?