I've got an angelfish that has always been pretty lively, would always come up to the glass whenever it saw me and was pretty eager to eat, but since the last water change something has happened to it and it's very inactive. It just sort of sits in the same few spots and doesn't move around very much, still eats but not as much as before. I've also noticed that it opens and closes its mouth all the time now and I don't remember it doing that. Anyone have any ideas what the reason may be?
Here's a video of it:
Here's a video of it: