So I noticed my cory just drifting through the tank. I panicked and thought he was dead, then I saw he was moving slightly. He drifted to the bottom and bumped against the gravel, then spun around and swam right to the top as fast as he could. He did like ten spins at top speed and then dive into a bunch of fake plants. Is this normal? Did he fall asleep or something? Is it something wrong? Is he just being silly?