I currently have 4 Serpae Tetra in my 45 Gallon tank, but one of them is very anti-social even after being in there for a month at least. I know there a schooling fish, but this one always hides in the corner while the other 3 are out swimming around. He is very pale almost like her is showing signs of stress.(Hiding + Very pale color) He does seem to come out when the light is off, but hide when it is on. So could the light be what is making him hide? Or is it something else? Or nothing at all?