foggy water

I have a 10 gallon tank. I have a biowheel filter system. My tank was
having an algae issue for some time which water changes wouldn't fix. The
stones were several years old so I thought perhaps this was the issue. I
changed the stones yesterday, and took out three gallons of water as well.
The water now 24 hours later looks clean but there is a fog look to it. The
smaller fish (tetras, catfish) are acting fine. The large angelfish while
swimming around and acknowledging me when I walk into the room, will not eat
and is hanging around the top of the water quite a bit (though not gasping
at the surface). What could be the issue with the foggy water? Is the
angel probably just stressed some? I will do a test on some of the water
parameters and post them separately.