A few days ago I noticed one of my angels started swimming with his nose up towards the top of the tank. Looks like when I'm feeding them and they are searching for food. When I go near the tank he greats me like all the other fish and sometimes he is swiming normally. But everytime I look at the tank, he's back in the corner with nose up. I have a 90 gallon tank. Amm. 0,nitries 0,nitrates 10(normally at 5). Temp runs about 80. I have a huge wet dry and a whisper triad 3000 on the tank. the fish is not gasping for air or scraping or really doing anything different, except for the vertical swimming. There is 3 other angels in the tank and they are fine. Anybody have any ideas if there is problem that I need to be worried about? I tried to get some pics of him. It's the angel in the back by the filter tube. Hangs out there all day til I go to the tank to feed then he seems fine.

