Woke up to feed my babies today and when I went to my angel tank he didn't eagerly come to the front of the tank when I came with food like he usually does. Upon further inspection I saw him in the back right corner of the tank hanging at an angle with his mouth near the top of the tank. he looks kind of black-ish on top and his fins are clenched shut. I have cories and tetras in there with him and they are doing fine. Params are right on (Nitrite/ammonia=0 nitrate is normal for me). It is hard to get a good look at him because 3/4 walls on the tank a have layer of algae on it (on purpose) so I just can't see him well. I have had him and the other guys in the tank for prolly about 6 months, if not more. Any ideas what may be wrong? I'm really concerned. He isn't eating and just sitting in the corner near the top.