One of my clowns, swims on his side at the top of the tank at some point during the night and then when the lights go on, he swims normally. First time I caught him I thought he was dying from getting roughed up by my other clown, so I isolated the "criminal" . A few nights later, I woke up middle of the night and guess what, he was swimming around on his side again, like he was doing the backstroke. I turned on the light and he acted like he was sleepwalking but started swimming normally. It is so funny! I felt bad for isolating the other fish, but now I know, it's normal for him. Clownies are fun to watch!