I know I am not giving a lot of information, but I have noticed one of my 4 Angelfish( the reast are swimming together and acting fine) has been singling itself out and is by itself on the other side of the tank. Now tonight it is at the bottom of the tank leaning(not laying).


I figure it is sick or going to die.

What are the most common possiblites and what can I do or buy right now or/and if it happens again in the future?