I have a Emerald Cory and I notice sometimes he just swim really fast to the top and go straight back down. Is that normal? Sometimes he look like he is dead since he doesn't move for a long time an then he suddenly does that. Very weird fish.
For other fish yes, but corys continue the behavior in well oxygenated water (if my tank is low o2 then there is a secret society of oxygen sucking gremlins hiding in the silicone).I thought it was them going to get air??? Maybe I'm wrong.
+1wait....A <---- (singular) cory? corys do like to be kept in a group of +6, (rarely a problem as they are fastidious little fish).