I use mystery snails to usually get rid of hydra, but some can be slackers. One mystery snail I’ve grown so attached to, I named it Larry, is always the lazy one of the batch. He did crawl out of his tank once, and since the tank is right next to my bed, he decided to go towards my face. Before I knew it, I woke up to discover I had a mystery snail in my face. But yeah, mystery snails can definitely get the job done.